1 /*-
2 * Copyright (c) 1990 The Regents of the University of California.
3 * 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 #if defined(LIBC_SCCS) && !defined(lint)
38 static char sccsid[] = "@(#)hash_buf.c 5.12 (Berkeley) 2/11/93";
39 #endif /* LIBC_SCCS and not lint */
40
41 /*
42 * PACKAGE: hash
43 *
44 * DESCRIPTION:
45 * Contains buffer management
46 *
47 * ROUTINES:
48 * External
49 * __buf_init
50 * __get_buf
51 * __buf_free
52 * __reclaim_buf
53 * Internal
54 * newbuf
55 */
56
57 #include <sys/param.h>
58
59 #include <errno.h>
60 #include <stdio.h>
61 #include <stdlib.h>
62 #ifdef DEBUG
63 #include <assert.h>
64 #endif
65
66 #include <db.h>
67 #include "hash.h"
68 #include "page.h"
69 #include "extern.h"
70
71 static BUFHEAD *newbuf __P((HTAB *, u_int, BUFHEAD *));
72
73 /* Unlink B from its place in the lru */
74 #define BUF_REMOVE(B) { \
75 (B)->prev->next = (B)->next; \
76 (B)->next->prev = (B)->prev; \
77 }
78
79 /* Insert B after P */
80 #define BUF_INSERT(B, P) { \
81 (B)->next = (P)->next; \
82 (B)->prev = (P); \
83 (P)->next = (B); \
84 (B)->next->prev = (B); \
85 }
86
87 #define MRU hashp->bufhead.next
88 #define LRU hashp->bufhead.prev
89
90 #define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead)
91 #define LRU_INSERT(B) BUF_INSERT((B), LRU)
92
93 /*
94 * We are looking for a buffer with address "addr". If prev_bp is NULL, then
95 * address is a bucket index. If prev_bp is not NULL, then it points to the
96 * page previous to an overflow page that we are trying to find.
97 *
98 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer
99 * be valid. Therefore, you must always verify that its address matches the
100 * address you are seeking.
101 */
102 extern BUFHEAD *
103 __get_buf(hashp, addr, prev_bp, newpage)
104 HTAB *hashp;
105 u_int addr;
106 BUFHEAD *prev_bp;
107 int newpage; /* If prev_bp set, indicates a new overflow page. */
108 {
109 register BUFHEAD *bp;
110 register u_int is_disk_mask;
111 register int is_disk, segment_ndx;
112 SEGMENT segp;
113
114 is_disk = 0;
115 is_disk_mask = 0;
116 if (prev_bp) {
117 bp = prev_bp->ovfl;
118 if (!bp || (bp->addr != addr))
119 bp = NULL;
120 if (!newpage)
121 is_disk = BUF_DISK;
122 } else {
123 /* Grab buffer out of directory */
124 segment_ndx = addr & (hashp->SGSIZE - 1);
125
126 /* valid segment ensured by __call_hash() */
127 segp = hashp->dir[addr >> hashp->SSHIFT];
128 #ifdef DEBUG
129 assert(segp != NULL);
130 #endif
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 *)((u_int)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(hashp,addr,prev_bp)158 newbuf(hashp, addr, prev_bp)
159 HTAB *hashp;
160 u_int addr;
161 BUFHEAD *prev_bp;
162 {
163 register BUFHEAD *bp; /* The buffer we're going to use */
164 register BUFHEAD *xbp; /* Temp pointer */
165 register BUFHEAD *next_xbp;
166 SEGMENT segp;
167 int segment_ndx;
168 u_short oaddr, *shortp;
169
170 oaddr = 0;
171 bp = LRU;
172 /*
173 * If LRU buffer is pinned, the buffer pool is too small. We need to
174 * allocate more buffers.
175 */
176 if (hashp->nbufs || (bp->flags & BUF_PIN)) {
177 /* Allocate a new one */
178 bp = malloc(sizeof(struct _bufhead));
179 if (!bp || !(bp->page = malloc(hashp->BSIZE)))
180 return (NULL);
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 = (u_short *)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 #ifdef DEBUG
213 assert(segp != NULL);
214 #endif
215
216 if (hashp->new_file &&
217 ((bp->flags & BUF_MOD) ||
218 ISDISK(segp[segment_ndx])))
219 segp[segment_ndx] = (BUFHEAD *)BUF_DISK;
220 else
221 segp[segment_ndx] = NULL;
222 }
223 /*
224 * Since overflow pages can only be access by means of
225 * their bucket, free overflow pages associated with
226 * this bucket.
227 */
228 for (xbp = bp; xbp->ovfl;) {
229 next_xbp = xbp->ovfl;
230 xbp->ovfl = 0;
231 xbp = next_xbp;
232
233 /* Check that ovfl pointer is up date. */
234 if (IS_BUCKET(xbp->flags) ||
235 (oaddr != xbp->addr))
236 break;
237
238 shortp = (u_short *)xbp->page;
239 if (shortp[0])
240 /* set before __put_page */
241 oaddr = shortp[shortp[0] - 1];
242 if ((xbp->flags & BUF_MOD) && __put_page(hashp,
243 xbp->page, xbp->addr, 0, 0))
244 return (NULL);
245 xbp->addr = 0;
246 xbp->flags = 0;
247 BUF_REMOVE(xbp);
248 LRU_INSERT(xbp);
249 }
250 }
251 }
252
253 /* Now assign this buffer */
254 bp->addr = addr;
255 #ifdef DEBUG1
256 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n",
257 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0);
258 #endif
259 bp->ovfl = NULL;
260 if (prev_bp) {
261 /*
262 * If prev_bp is set, this is an overflow page, hook it in to
263 * the buffer overflow links.
264 */
265 #ifdef DEBUG1
266 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n",
267 prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0),
268 (bp ? bp->addr : 0));
269 #endif
270 prev_bp->ovfl = bp;
271 bp->flags = 0;
272 } else
273 bp->flags = BUF_BUCKET;
274 MRU_INSERT(bp);
275 return (bp);
276 }
277
278 extern void
279 __buf_init(hashp, nbytes)
280 HTAB *hashp;
281 int nbytes;
282 {
283 BUFHEAD *bfp;
284 int npages;
285
286 bfp = &(hashp->bufhead);
287 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT;
288 npages = MAX(npages, MIN_BUFFERS);
289
290 hashp->nbufs = npages;
291 bfp->next = bfp;
292 bfp->prev = bfp;
293 /*
294 * This space is calloc'd so these are already null.
295 *
296 * bfp->ovfl = NULL;
297 * bfp->flags = 0;
298 * bfp->page = NULL;
299 * bfp->addr = 0;
300 */
301 }
302
303 extern int
304 __buf_free(hashp, do_free, to_disk)
305 HTAB *hashp;
306 int do_free, to_disk;
307 {
308 BUFHEAD *bp;
309
310 /* Need to make sure that buffer manager has been initialized */
311 if (!LRU)
312 return (0);
313 for (bp = LRU; bp != &hashp->bufhead;) {
314 /* Check that the buffer is valid */
315 if (bp->addr || IS_BUCKET(bp->flags)) {
316 if (to_disk && (bp->flags & BUF_MOD) &&
317 __put_page(hashp, bp->page,
318 bp->addr, IS_BUCKET(bp->flags), 0))
319 return (-1);
320 }
321 /* Check if we are freeing stuff */
322 if (do_free) {
323 if (bp->page)
324 free(bp->page);
325 BUF_REMOVE(bp);
326 free(bp);
327 bp = LRU;
328 } else
329 bp = bp->prev;
330 }
331 return (0);
332 }
333
334 extern void
335 __reclaim_buf(hashp, bp)
336 HTAB *hashp;
337 BUFHEAD *bp;
338 {
339 bp->ovfl = 0;
340 bp->addr = 0;
341 bp->flags = 0;
342 BUF_REMOVE(bp);
343 LRU_INSERT(bp);
344 }
345