1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
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 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 * PACKAGE: hash
40 *
41 * DESCRIPTION:
42 * Contains buffer management
43 *
44 * ROUTINES:
45 * External
46 * __buf_init
47 * __get_buf
48 * __buf_free
49 * __reclaim_buf
50 * Internal
51 * newbuf
52 */
53
54 #include <sys/param.h>
55
56 #include <stddef.h>
57 #include <stdio.h>
58 #include <stdlib.h>
59 #include <string.h>
60
61 #ifdef DEBUG
62 #include <assert.h>
63 #endif
64
65 #include <db.h>
66 #include "hash.h"
67 #include "page.h"
68 #include "extern.h"
69
70 static BUFHEAD *newbuf(HTAB *, u_int32_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 /*
93 * We are looking for a buffer with address "addr". If prev_bp is NULL, then
94 * address is a bucket index. If prev_bp is not NULL, then it points to the
95 * page previous to an overflow page that we are trying to find.
96 *
97 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer
98 * be valid. Therefore, you must always verify that its address matches the
99 * address you are seeking.
100 */
101 BUFHEAD *
__get_buf(HTAB * hashp,u_int32_t addr,BUFHEAD * prev_bp,int newpage)102 __get_buf(HTAB *hashp, u_int32_t addr,
103 BUFHEAD *prev_bp, /* If prev_bp set, indicates a new overflow page. */
104 int newpage)
105 {
106 BUFHEAD *bp;
107 u_int32_t is_disk_mask;
108 int is_disk, segment_ndx;
109 SEGMENT segp;
110
111 is_disk = 0;
112 is_disk_mask = 0;
113 if (prev_bp) {
114 bp = prev_bp->ovfl;
115 if (!bp || (bp->addr != addr))
116 bp = NULL;
117 if (!newpage)
118 is_disk = BUF_DISK;
119 } else {
120 /* Grab buffer out of directory */
121 segment_ndx = addr & (hashp->SGSIZE - 1);
122
123 /* valid segment ensured by __call_hash() */
124 segp = hashp->dir[addr >> hashp->SSHIFT];
125 #ifdef DEBUG
126 assert(segp != NULL);
127 #endif
128 bp = PTROF(segp[segment_ndx]);
129 is_disk_mask = ISDISK(segp[segment_ndx]);
130 is_disk = is_disk_mask || !hashp->new_file;
131 }
132
133 if (!bp) {
134 bp = newbuf(hashp, addr, prev_bp);
135 if (!bp ||
136 __get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0))
137 return (NULL);
138 if (!prev_bp)
139 segp[segment_ndx] =
140 (BUFHEAD *)((intptr_t)bp | is_disk_mask);
141 } else {
142 BUF_REMOVE(bp);
143 MRU_INSERT(bp);
144 }
145 return (bp);
146 }
147
148 /*
149 * We need a buffer for this page. Either allocate one, or evict a resident
150 * one (if we have as many buffers as we're allowed) and put this one in.
151 *
152 * If newbuf finds an error (returning NULL), it also sets errno.
153 */
154 static BUFHEAD *
newbuf(HTAB * hashp,u_int32_t addr,BUFHEAD * prev_bp)155 newbuf(HTAB *hashp, u_int32_t addr, BUFHEAD *prev_bp)
156 {
157 BUFHEAD *bp; /* The buffer we're going to use */
158 BUFHEAD *xbp; /* Temp pointer */
159 BUFHEAD *next_xbp;
160 SEGMENT segp;
161 int segment_ndx;
162 u_int16_t oaddr, *shortp;
163
164 oaddr = 0;
165 bp = LRU;
166
167 /* It is bad to overwrite the page under the cursor. */
168 if (bp == hashp->cpage) {
169 BUF_REMOVE(bp);
170 MRU_INSERT(bp);
171 bp = LRU;
172 }
173
174 /* If prev_bp is part of bp overflow, create a new buffer. */
175 if (hashp->nbufs == 0 && prev_bp && bp->ovfl) {
176 BUFHEAD *ovfl;
177
178 for (ovfl = bp->ovfl; ovfl ; ovfl = ovfl->ovfl) {
179 if (ovfl == prev_bp) {
180 hashp->nbufs++;
181 break;
182 }
183 }
184 }
185
186 /*
187 * If LRU buffer is pinned, the buffer pool is too small. We need to
188 * allocate more buffers.
189 */
190 if (hashp->nbufs || (bp->flags & BUF_PIN) || bp == hashp->cpage) {
191 /* Allocate a new one */
192 if ((bp = (BUFHEAD *)calloc(1, sizeof(BUFHEAD))) == NULL)
193 return (NULL);
194 if ((bp->page = (char *)calloc(1, hashp->BSIZE)) == NULL) {
195 free(bp);
196 return (NULL);
197 }
198 if (hashp->nbufs)
199 hashp->nbufs--;
200 } else {
201 /* Kick someone out */
202 BUF_REMOVE(bp);
203 /*
204 * If this is an overflow page with addr 0, it's already been
205 * flushed back in an overflow chain and initialized.
206 */
207 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) {
208 /*
209 * Set oaddr before __put_page so that you get it
210 * before bytes are swapped.
211 */
212 shortp = (u_int16_t *)bp->page;
213 if (shortp[0])
214 oaddr = shortp[shortp[0] - 1];
215 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page,
216 bp->addr, (int)IS_BUCKET(bp->flags), 0))
217 return (NULL);
218 /*
219 * Update the pointer to this page (i.e. invalidate it).
220 *
221 * If this is a new file (i.e. we created it at open
222 * time), make sure that we mark pages which have been
223 * written to disk so we retrieve them from disk later,
224 * rather than allocating new pages.
225 */
226 if (IS_BUCKET(bp->flags)) {
227 segment_ndx = bp->addr & (hashp->SGSIZE - 1);
228 segp = hashp->dir[bp->addr >> hashp->SSHIFT];
229 #ifdef DEBUG
230 assert(segp != NULL);
231 #endif
232
233 if (hashp->new_file &&
234 ((bp->flags & BUF_MOD) ||
235 ISDISK(segp[segment_ndx])))
236 segp[segment_ndx] = (BUFHEAD *)BUF_DISK;
237 else
238 segp[segment_ndx] = NULL;
239 }
240 /*
241 * Since overflow pages can only be access by means of
242 * their bucket, free overflow pages associated with
243 * this bucket.
244 */
245 for (xbp = bp; xbp->ovfl;) {
246 next_xbp = xbp->ovfl;
247 xbp->ovfl = NULL;
248 xbp = next_xbp;
249
250 /* Check that ovfl pointer is up date. */
251 if (IS_BUCKET(xbp->flags) ||
252 (oaddr != xbp->addr))
253 break;
254
255 shortp = (u_int16_t *)xbp->page;
256 if (shortp[0])
257 /* set before __put_page */
258 oaddr = shortp[shortp[0] - 1];
259 if ((xbp->flags & BUF_MOD) && __put_page(hashp,
260 xbp->page, xbp->addr, 0, 0))
261 return (NULL);
262 xbp->addr = 0;
263 xbp->flags = 0;
264 BUF_REMOVE(xbp);
265 LRU_INSERT(xbp);
266 }
267 }
268 }
269
270 /* Now assign this buffer */
271 bp->addr = addr;
272 #ifdef DEBUG1
273 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n",
274 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0);
275 #endif
276 bp->ovfl = NULL;
277 if (prev_bp) {
278 /*
279 * If prev_bp is set, this is an overflow page, hook it in to
280 * the buffer overflow links.
281 */
282 #ifdef DEBUG1
283 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n",
284 prev_bp->addr, (prev_bp->ovfl ? prev_bp->ovfl->addr : 0),
285 (bp ? bp->addr : 0));
286 #endif
287 prev_bp->ovfl = bp;
288 bp->flags = 0;
289 } else
290 bp->flags = BUF_BUCKET;
291 MRU_INSERT(bp);
292 return (bp);
293 }
294
295 void
__buf_init(HTAB * hashp,int nbytes)296 __buf_init(HTAB *hashp, int nbytes)
297 {
298 BUFHEAD *bfp;
299 int npages;
300
301 bfp = &(hashp->bufhead);
302 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT;
303 npages = MAX(npages, MIN_BUFFERS);
304
305 hashp->nbufs = npages;
306 bfp->next = bfp;
307 bfp->prev = bfp;
308 /*
309 * This space is calloc'd so these are already null.
310 *
311 * bfp->ovfl = NULL;
312 * bfp->flags = 0;
313 * bfp->page = NULL;
314 * bfp->addr = 0;
315 */
316 }
317
318 int
__buf_free(HTAB * hashp,int do_free,int to_disk)319 __buf_free(HTAB *hashp, int do_free, int to_disk)
320 {
321 BUFHEAD *bp;
322
323 /* Need to make sure that buffer manager has been initialized */
324 if (!LRU)
325 return (0);
326 for (bp = LRU; bp != &hashp->bufhead;) {
327 /* Check that the buffer is valid */
328 if (bp->addr || IS_BUCKET(bp->flags)) {
329 if (to_disk && (bp->flags & BUF_MOD) &&
330 __put_page(hashp, bp->page,
331 bp->addr, IS_BUCKET(bp->flags), 0))
332 return (-1);
333 }
334 /* Check if we are freeing stuff */
335 if (do_free) {
336 if (bp->page) {
337 (void)memset(bp->page, 0, hashp->BSIZE);
338 free(bp->page);
339 }
340 BUF_REMOVE(bp);
341 free(bp);
342 bp = LRU;
343 } else
344 bp = bp->prev;
345 }
346 return (0);
347 }
348
349 void
__reclaim_buf(HTAB * hashp,BUFHEAD * bp)350 __reclaim_buf(HTAB *hashp, BUFHEAD *bp)
351 {
352 bp->ovfl = NULL;
353 bp->addr = 0;
354 bp->flags = 0;
355 BUF_REMOVE(bp);
356 LRU_INSERT(bp);
357 }
358