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. All advertising materials mentioning features or use of this software
17 * must display the following acknowledgement:
18 * This product includes software developed by the University of
19 * California, Berkeley and its contributors.
20 * 4. Neither the name of the University nor the names of its contributors
21 * may be used to endorse or promote products derived from this software
22 * without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37 #include <sys/param.h>
38 #if defined(LIBC_SCCS) && !defined(lint)
39 static char sccsid[] = "@(#)hash_buf.c 8.5 (Berkeley) 7/15/94";
40 #endif /* LIBC_SCCS and not lint */
41 #include <sys/cdefs.h>
42
43 /*
44 * PACKAGE: hash
45 *
46 * DESCRIPTION:
47 * Contains buffer management
48 *
49 * ROUTINES:
50 * External
51 * __buf_init
52 * __get_buf
53 * __buf_free
54 * __reclaim_buf
55 * Internal
56 * newbuf
57 */
58
59 #include <sys/param.h>
60
61 #include <stddef.h>
62 #include <stdio.h>
63 #include <stdlib.h>
64
65 #ifdef DEBUG
66 #include <assert.h>
67 #endif
68
69 #include "db_local.h"
70 #include "hash.h"
71 #include "page.h"
72 #include "extern.h"
73
74 static BUFHEAD *newbuf(HTAB *, __uint32_t, BUFHEAD *);
75
76 /* Unlink B from its place in the lru */
77 #define BUF_REMOVE(B) { \
78 (B)->prev->next = (B)->next; \
79 (B)->next->prev = (B)->prev; \
80 }
81
82 /* Insert B after P */
83 #define BUF_INSERT(B, P) { \
84 (B)->next = (P)->next; \
85 (B)->prev = (P); \
86 (P)->next = (B); \
87 (B)->next->prev = (B); \
88 }
89
90 #define MRU hashp->bufhead.next
91 #define LRU hashp->bufhead.prev
92
93 #define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead)
94 #define LRU_INSERT(B) BUF_INSERT((B), LRU)
95
96 /* Macros for min/max. */
97 #ifndef MIN
98 #define MIN(a,b) (((a)<(b))?(a):(b))
99 #endif
100 #ifndef MAX
101 #define MAX(a,b) (((a)>(b))?(a):(b))
102 #endif
103
104 /*
105 * We are looking for a buffer with address "addr". If prev_bp is NULL, then
106 * address is a bucket index. If prev_bp is not NULL, then it points to the
107 * page previous to an overflow page that we are trying to find.
108 *
109 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer
110 * be valid. Therefore, you must always verify that its address matches the
111 * address you are seeking.
112 */
113 extern BUFHEAD *
114 __get_buf(hashp, addr, prev_bp, newpage)
115 HTAB *hashp;
116 __uint32_t addr;
117 BUFHEAD *prev_bp;
118 int newpage; /* If prev_bp set, indicates a new overflow page. */
119 {
120 BUFHEAD *bp;
121 __uint32_t is_disk_mask;
122 int is_disk, segment_ndx = 0;
123 SEGMENT segp = NULL;
124
125 is_disk = 0;
126 is_disk_mask = 0;
127 if (prev_bp) {
128 bp = prev_bp->ovfl;
129 if (!bp || (bp->addr != addr))
130 bp = NULL;
131 if (!newpage)
132 is_disk = BUF_DISK;
133 } else {
134 /* Grab buffer out of directory */
135 segment_ndx = addr & (hashp->SGSIZE - 1);
136
137 /* valid segment ensured by __call_hash() */
138 segp = hashp->dir[addr >> hashp->SSHIFT];
139 #ifdef DEBUG
140 assert(segp != NULL);
141 #endif
142 bp = PTROF(segp[segment_ndx]);
143 is_disk_mask = ISDISK(segp[segment_ndx]);
144 is_disk = is_disk_mask || !hashp->new_file;
145 }
146
147 if (!bp) {
148 bp = newbuf(hashp, addr, prev_bp);
149 if (!bp ||
150 __get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0))
151 return (NULL);
152 if (!prev_bp)
153 segp[segment_ndx] =
154 (BUFHEAD *)((ptrdiff_t)bp | is_disk_mask);
155 } else {
156 BUF_REMOVE(bp);
157 MRU_INSERT(bp);
158 }
159 return (bp);
160 }
161
162 /*
163 * We need a buffer for this page. Either allocate one, or evict a resident
164 * one (if we have as many buffers as we're allowed) and put this one in.
165 *
166 * If newbuf finds an error (returning NULL), it also sets errno.
167 */
168 static BUFHEAD *
newbuf(hashp,addr,prev_bp)169 newbuf(hashp, addr, prev_bp)
170 HTAB *hashp;
171 __uint32_t addr;
172 BUFHEAD *prev_bp;
173 {
174 BUFHEAD *bp; /* The buffer we're going to use */
175 BUFHEAD *xbp; /* Temp pointer */
176 BUFHEAD *next_xbp;
177 SEGMENT segp;
178 int segment_ndx;
179 __uint16_t oaddr, *shortp;
180
181 oaddr = 0;
182 bp = LRU;
183 /*
184 * If LRU buffer is pinned, the buffer pool is too small. We need to
185 * allocate more buffers.
186 */
187 if (hashp->nbufs || (bp->flags & BUF_PIN)) {
188 /* Allocate a new one */
189 if ((bp = (BUFHEAD *)malloc(sizeof(BUFHEAD))) == NULL)
190 return (NULL);
191 #ifdef PURIFY
192 memset(bp, 0xff, sizeof(BUFHEAD));
193 #endif
194 if ((bp->page = (char *)malloc(hashp->BSIZE)) == NULL) {
195 free(bp);
196 return (NULL);
197 }
198 #ifdef PURIFY
199 memset(bp->page, 0xff, hashp->BSIZE);
200 #endif
201 if (hashp->nbufs)
202 hashp->nbufs--;
203 } else {
204 /* Kick someone out */
205 BUF_REMOVE(bp);
206 /*
207 * If this is an overflow page with addr 0, it's already been
208 * flushed back in an overflow chain and initialized.
209 */
210 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) {
211 /*
212 * Set oaddr before __put_page so that you get it
213 * before bytes are swapped.
214 */
215 shortp = (__uint16_t *)bp->page;
216 if (shortp[0])
217 oaddr = shortp[shortp[0] - 1];
218 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page,
219 bp->addr, (int)IS_BUCKET(bp->flags), 0))
220 return (NULL);
221 /*
222 * Update the pointer to this page (i.e. invalidate it).
223 *
224 * If this is a new file (i.e. we created it at open
225 * time), make sure that we mark pages which have been
226 * written to disk so we retrieve them from disk later,
227 * rather than allocating new pages.
228 */
229 if (IS_BUCKET(bp->flags)) {
230 segment_ndx = bp->addr & (hashp->SGSIZE - 1);
231 segp = hashp->dir[bp->addr >> hashp->SSHIFT];
232 #ifdef DEBUG
233 assert(segp != NULL);
234 #endif
235
236 if (hashp->new_file &&
237 ((bp->flags & BUF_MOD) ||
238 ISDISK(segp[segment_ndx])))
239 segp[segment_ndx] = (BUFHEAD *)BUF_DISK;
240 else
241 segp[segment_ndx] = NULL;
242 }
243 /*
244 * Since overflow pages can only be access by means of
245 * their bucket, free overflow pages associated with
246 * this bucket.
247 */
248 for (xbp = bp; xbp->ovfl;) {
249 next_xbp = xbp->ovfl;
250 xbp->ovfl = 0;
251 xbp = next_xbp;
252
253 /* Check that ovfl pointer is up date. */
254 if (IS_BUCKET(xbp->flags) ||
255 (oaddr != xbp->addr))
256 break;
257
258 shortp = (__uint16_t *)xbp->page;
259 if (shortp[0])
260 /* set before __put_page */
261 oaddr = shortp[shortp[0] - 1];
262 if ((xbp->flags & BUF_MOD) && __put_page(hashp,
263 xbp->page, xbp->addr, 0, 0))
264 return (NULL);
265 xbp->addr = 0;
266 xbp->flags = 0;
267 BUF_REMOVE(xbp);
268 LRU_INSERT(xbp);
269 }
270 }
271 }
272
273 /* Now assign this buffer */
274 bp->addr = addr;
275 #ifdef DEBUG1
276 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n",
277 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0);
278 #endif
279 bp->ovfl = NULL;
280 if (prev_bp) {
281 /*
282 * If prev_bp is set, this is an overflow page, hook it in to
283 * the buffer overflow links.
284 */
285 #ifdef DEBUG1
286 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n",
287 prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0),
288 (bp ? bp->addr : 0));
289 #endif
290 prev_bp->ovfl = bp;
291 bp->flags = 0;
292 } else
293 bp->flags = BUF_BUCKET;
294 MRU_INSERT(bp);
295 return (bp);
296 }
297
298 extern void
299 __buf_init(hashp, nbytes)
300 HTAB *hashp;
301 int nbytes;
302 {
303 BUFHEAD *bfp;
304 int npages;
305
306 bfp = &(hashp->bufhead);
307 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT;
308 npages = MAX(npages, MIN_BUFFERS);
309
310 hashp->nbufs = npages;
311 bfp->next = bfp;
312 bfp->prev = bfp;
313 /*
314 * This space is calloc'd so these are already null.
315 *
316 * bfp->ovfl = NULL;
317 * bfp->flags = 0;
318 * bfp->page = NULL;
319 * bfp->addr = 0;
320 */
321 }
322
323 extern int
324 __buf_free(hashp, do_free, to_disk)
325 HTAB *hashp;
326 int do_free, to_disk;
327 {
328 BUFHEAD *bp;
329
330 /* Need to make sure that buffer manager has been initialized */
331 if (!LRU)
332 return (0);
333 for (bp = LRU; bp != &hashp->bufhead;) {
334 /* Check that the buffer is valid */
335 if (bp->addr || IS_BUCKET(bp->flags)) {
336 if (to_disk && (bp->flags & BUF_MOD) &&
337 __put_page(hashp, bp->page,
338 bp->addr, IS_BUCKET(bp->flags), 0))
339 return (-1);
340 }
341 /* Check if we are freeing stuff */
342 if (do_free) {
343 if (bp->page)
344 free(bp->page);
345 BUF_REMOVE(bp);
346 free(bp);
347 bp = LRU;
348 } else
349 bp = bp->prev;
350 }
351 return (0);
352 }
353
354 extern void
355 __reclaim_buf(hashp, bp)
356 HTAB *hashp;
357 BUFHEAD *bp;
358 {
359 bp->ovfl = 0;
360 bp->addr = 0;
361 bp->flags = 0;
362 BUF_REMOVE(bp);
363 LRU_INSERT(bp);
364 }
365