1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
|
/*-
* Copyright (c) 1990, 1993, 1994
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Margo Seltzer.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)hash_buf.c 8.5 (Berkeley) 7/15/94";
#endif /* LIBC_SCCS and not lint */
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
/*
* PACKAGE: hash
*
* DESCRIPTION:
* Contains buffer management
*
* ROUTINES:
* External
* __buf_init
* __get_buf
* __buf_free
* __reclaim_buf
* Internal
* newbuf
*/
#include <sys/param.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifdef DEBUG
#include <assert.h>
#endif
#include <db.h>
#include "hash.h"
#include "page.h"
#include "extern.h"
static BUFHEAD *newbuf(HTAB *, u_int32_t, BUFHEAD *);
/* Unlink B from its place in the lru */
#define BUF_REMOVE(B) { \
(B)->prev->next = (B)->next; \
(B)->next->prev = (B)->prev; \
}
/* Insert B after P */
#define BUF_INSERT(B, P) { \
(B)->next = (P)->next; \
(B)->prev = (P); \
(P)->next = (B); \
(B)->next->prev = (B); \
}
#define MRU hashp->bufhead.next
#define LRU hashp->bufhead.prev
#define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead)
#define LRU_INSERT(B) BUF_INSERT((B), LRU)
/*
* We are looking for a buffer with address "addr". If prev_bp is NULL, then
* address is a bucket index. If prev_bp is not NULL, then it points to the
* page previous to an overflow page that we are trying to find.
*
* CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer
* be valid. Therefore, you must always verify that its address matches the
* address you are seeking.
*/
BUFHEAD *
__get_buf(HTAB *hashp, u_int32_t addr,
BUFHEAD *prev_bp, /* If prev_bp set, indicates a new overflow page. */
int newpage)
{
BUFHEAD *bp;
u_int32_t is_disk_mask;
int is_disk, segment_ndx;
SEGMENT segp;
is_disk = 0;
is_disk_mask = 0;
if (prev_bp) {
bp = prev_bp->ovfl;
if (!bp || (bp->addr != addr))
bp = NULL;
if (!newpage)
is_disk = BUF_DISK;
} else {
/* Grab buffer out of directory */
segment_ndx = addr & (hashp->SGSIZE - 1);
/* valid segment ensured by __call_hash() */
segp = hashp->dir[addr >> hashp->SSHIFT];
#ifdef DEBUG
assert(segp != NULL);
#endif
bp = PTROF(segp[segment_ndx]);
is_disk_mask = ISDISK(segp[segment_ndx]);
is_disk = is_disk_mask || !hashp->new_file;
}
if (!bp) {
bp = newbuf(hashp, addr, prev_bp);
if (!bp ||
__get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0))
return (NULL);
if (!prev_bp)
segp[segment_ndx] =
(BUFHEAD *)((ptrdiff_t)bp | is_disk_mask);
} else {
BUF_REMOVE(bp);
MRU_INSERT(bp);
}
return (bp);
}
/*
* We need a buffer for this page. Either allocate one, or evict a resident
* one (if we have as many buffers as we're allowed) and put this one in.
*
* If newbuf finds an error (returning NULL), it also sets errno.
*/
static BUFHEAD *
newbuf(HTAB *hashp, u_int32_t addr, BUFHEAD *prev_bp)
{
BUFHEAD *bp; /* The buffer we're going to use */
BUFHEAD *xbp; /* Temp pointer */
BUFHEAD *next_xbp;
SEGMENT segp;
int segment_ndx;
u_int16_t oaddr, *shortp;
oaddr = 0;
bp = LRU;
/* It is bad to overwrite the page under the cursor. */
if (bp == hashp->cpage) {
BUF_REMOVE(bp);
MRU_INSERT(bp);
bp = LRU;
}
/* If prev_bp is part of bp overflow, create a new buffer. */
if (hashp->nbufs == 0 && prev_bp && bp->ovfl) {
BUFHEAD *ovfl;
for (ovfl = bp->ovfl; ovfl ; ovfl = ovfl->ovfl) {
if (ovfl == prev_bp) {
hashp->nbufs++;
break;
}
}
}
/*
* If LRU buffer is pinned, the buffer pool is too small. We need to
* allocate more buffers.
*/
if (hashp->nbufs || (bp->flags & BUF_PIN) || bp == hashp->cpage) {
/* Allocate a new one */
if ((bp = (BUFHEAD *)calloc(1, sizeof(BUFHEAD))) == NULL)
return (NULL);
if ((bp->page = (char *)calloc(1, hashp->BSIZE)) == NULL) {
free(bp);
return (NULL);
}
if (hashp->nbufs)
hashp->nbufs--;
} else {
/* Kick someone out */
BUF_REMOVE(bp);
/*
* If this is an overflow page with addr 0, it's already been
* flushed back in an overflow chain and initialized.
*/
if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) {
/*
* Set oaddr before __put_page so that you get it
* before bytes are swapped.
*/
shortp = (u_int16_t *)bp->page;
if (shortp[0])
oaddr = shortp[shortp[0] - 1];
if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page,
bp->addr, (int)IS_BUCKET(bp->flags), 0))
return (NULL);
/*
* Update the pointer to this page (i.e. invalidate it).
*
* If this is a new file (i.e. we created it at open
* time), make sure that we mark pages which have been
* written to disk so we retrieve them from disk later,
* rather than allocating new pages.
*/
if (IS_BUCKET(bp->flags)) {
segment_ndx = bp->addr & (hashp->SGSIZE - 1);
segp = hashp->dir[bp->addr >> hashp->SSHIFT];
#ifdef DEBUG
assert(segp != NULL);
#endif
if (hashp->new_file &&
((bp->flags & BUF_MOD) ||
ISDISK(segp[segment_ndx])))
segp[segment_ndx] = (BUFHEAD *)BUF_DISK;
else
segp[segment_ndx] = NULL;
}
/*
* Since overflow pages can only be access by means of
* their bucket, free overflow pages associated with
* this bucket.
*/
for (xbp = bp; xbp->ovfl;) {
next_xbp = xbp->ovfl;
xbp->ovfl = 0;
xbp = next_xbp;
/* Check that ovfl pointer is up date. */
if (IS_BUCKET(xbp->flags) ||
(oaddr != xbp->addr))
break;
shortp = (u_int16_t *)xbp->page;
if (shortp[0])
/* set before __put_page */
oaddr = shortp[shortp[0] - 1];
if ((xbp->flags & BUF_MOD) && __put_page(hashp,
xbp->page, xbp->addr, 0, 0))
return (NULL);
xbp->addr = 0;
xbp->flags = 0;
BUF_REMOVE(xbp);
LRU_INSERT(xbp);
}
}
}
/* Now assign this buffer */
bp->addr = addr;
#ifdef DEBUG1
(void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n",
bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0);
#endif
bp->ovfl = NULL;
if (prev_bp) {
/*
* If prev_bp is set, this is an overflow page, hook it in to
* the buffer overflow links.
*/
#ifdef DEBUG1
(void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n",
prev_bp->addr, (prev_bp->ovfl ? prev_bp->ovfl->addr : 0),
(bp ? bp->addr : 0));
#endif
prev_bp->ovfl = bp;
bp->flags = 0;
} else
bp->flags = BUF_BUCKET;
MRU_INSERT(bp);
return (bp);
}
void
__buf_init(HTAB *hashp, int nbytes)
{
BUFHEAD *bfp;
int npages;
bfp = &(hashp->bufhead);
npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT;
npages = MAX(npages, MIN_BUFFERS);
hashp->nbufs = npages;
bfp->next = bfp;
bfp->prev = bfp;
/*
* This space is calloc'd so these are already null.
*
* bfp->ovfl = NULL;
* bfp->flags = 0;
* bfp->page = NULL;
* bfp->addr = 0;
*/
}
int
__buf_free(HTAB *hashp, int do_free, int to_disk)
{
BUFHEAD *bp;
/* Need to make sure that buffer manager has been initialized */
if (!LRU)
return (0);
for (bp = LRU; bp != &hashp->bufhead;) {
/* Check that the buffer is valid */
if (bp->addr || IS_BUCKET(bp->flags)) {
if (to_disk && (bp->flags & BUF_MOD) &&
__put_page(hashp, bp->page,
bp->addr, IS_BUCKET(bp->flags), 0))
return (-1);
}
/* Check if we are freeing stuff */
if (do_free) {
if (bp->page) {
(void)memset(bp->page, 0, hashp->BSIZE);
free(bp->page);
}
BUF_REMOVE(bp);
free(bp);
bp = LRU;
} else
bp = bp->prev;
}
return (0);
}
void
__reclaim_buf(HTAB *hashp, BUFHEAD *bp)
{
bp->ovfl = 0;
bp->addr = 0;
bp->flags = 0;
BUF_REMOVE(bp);
LRU_INSERT(bp);
}
|