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 #include <sys/cdefs.h>
39 __FBSDID("$FreeBSD$");
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 <stddef.h>
60 #include <stdio.h>
61 #include <stdlib.h>
62 #include <string.h>
63
64 #ifdef DEBUG
65 #include <assert.h>
66 #endif
67
68 #include <db.h>
69 #include "hash.h"
70 #include "page.h"
71 #include "extern.h"
72
73 static BUFHEAD *newbuf(HTAB *, u_int32_t, BUFHEAD *);
74
75 /* Unlink B from its place in the lru */
76 #define BUF_REMOVE(B) { \
77 (B)->prev->next = (B)->next; \
78 (B)->next->prev = (B)->prev; \
79 }
80
81 /* Insert B after P */
82 #define BUF_INSERT(B, P) { \
83 (B)->next = (P)->next; \
84 (B)->prev = (P); \
85 (P)->next = (B); \
86 (B)->next->prev = (B); \
87 }
88
89 #define MRU hashp->bufhead.next
90 #define LRU hashp->bufhead.prev
91
92 #define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead)
93 #define LRU_INSERT(B) BUF_INSERT((B), LRU)
94
95 /*
96 * We are looking for a buffer with address "addr". If prev_bp is NULL, then
97 * address is a bucket index. If prev_bp is not NULL, then it points to the
98 * page previous to an overflow page that we are trying to find.
99 *
100 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer
101 * be valid. Therefore, you must always verify that its address matches the
102 * address you are seeking.
103 */
104 BUFHEAD *
__get_buf(HTAB * hashp,u_int32_t addr,BUFHEAD * prev_bp,int newpage)105 __get_buf(HTAB *hashp, u_int32_t addr,
106 BUFHEAD *prev_bp, /* If prev_bp set, indicates a new overflow page. */
107 int newpage)
108 {
109 BUFHEAD *bp;
110 u_int32_t is_disk_mask;
111 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 *)((intptr_t)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(HTAB * hashp,u_int32_t addr,BUFHEAD * prev_bp)158 newbuf(HTAB *hashp, u_int32_t addr, BUFHEAD *prev_bp)
159 {
160 BUFHEAD *bp; /* The buffer we're going to use */
161 BUFHEAD *xbp; /* Temp pointer */
162 BUFHEAD *next_xbp;
163 SEGMENT segp;
164 int segment_ndx;
165 u_int16_t oaddr, *shortp;
166
167 oaddr = 0;
168 bp = LRU;
169
170 /* It is bad to overwrite the page under the cursor. */
171 if (bp == hashp->cpage) {
172 BUF_REMOVE(bp);
173 MRU_INSERT(bp);
174 bp = LRU;
175 }
176
177 /* If prev_bp is part of bp overflow, create a new buffer. */
178 if (hashp->nbufs == 0 && prev_bp && bp->ovfl) {
179 BUFHEAD *ovfl;
180
181 for (ovfl = bp->ovfl; ovfl ; ovfl = ovfl->ovfl) {
182 if (ovfl == prev_bp) {
183 hashp->nbufs++;
184 break;
185 }
186 }
187 }
188
189 /*
190 * If LRU buffer is pinned, the buffer pool is too small. We need to
191 * allocate more buffers.
192 */
193 if (hashp->nbufs || (bp->flags & BUF_PIN) || bp == hashp->cpage) {
194 /* Allocate a new one */
195 if ((bp = (BUFHEAD *)calloc(1, sizeof(BUFHEAD))) == NULL)
196 return (NULL);
197 if ((bp->page = (char *)calloc(1, hashp->BSIZE)) == NULL) {
198 free(bp);
199 return (NULL);
200 }
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 = (u_int16_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 = NULL;
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 = (u_int16_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 ? prev_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 void
__buf_init(HTAB * hashp,int nbytes)299 __buf_init(HTAB *hashp, int nbytes)
300 {
301 BUFHEAD *bfp;
302 int npages;
303
304 bfp = &(hashp->bufhead);
305 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT;
306 npages = MAX(npages, MIN_BUFFERS);
307
308 hashp->nbufs = npages;
309 bfp->next = bfp;
310 bfp->prev = bfp;
311 /*
312 * This space is calloc'd so these are already null.
313 *
314 * bfp->ovfl = NULL;
315 * bfp->flags = 0;
316 * bfp->page = NULL;
317 * bfp->addr = 0;
318 */
319 }
320
321 int
__buf_free(HTAB * hashp,int do_free,int to_disk)322 __buf_free(HTAB *hashp, int do_free, int to_disk)
323 {
324 BUFHEAD *bp;
325
326 /* Need to make sure that buffer manager has been initialized */
327 if (!LRU)
328 return (0);
329 for (bp = LRU; bp != &hashp->bufhead;) {
330 /* Check that the buffer is valid */
331 if (bp->addr || IS_BUCKET(bp->flags)) {
332 if (to_disk && (bp->flags & BUF_MOD) &&
333 __put_page(hashp, bp->page,
334 bp->addr, IS_BUCKET(bp->flags), 0))
335 return (-1);
336 }
337 /* Check if we are freeing stuff */
338 if (do_free) {
339 if (bp->page) {
340 (void)memset(bp->page, 0, hashp->BSIZE);
341 free(bp->page);
342 }
343 BUF_REMOVE(bp);
344 free(bp);
345 bp = LRU;
346 } else
347 bp = bp->prev;
348 }
349 return (0);
350 }
351
352 void
__reclaim_buf(HTAB * hashp,BUFHEAD * bp)353 __reclaim_buf(HTAB *hashp, BUFHEAD *bp)
354 {
355 bp->ovfl = NULL;
356 bp->addr = 0;
357 bp->flags = 0;
358 BUF_REMOVE(bp);
359 LRU_INSERT(bp);
360 }
361