aboutsummaryrefslogtreecommitdiff
path: root/db2/log/log_get.c
blob: de81519a7cec46a336c6663a4248632c76fb76b2 (plain)
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
/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996, 1997, 1998
 *	Sleepycat Software.  All rights reserved.
 */
#include "config.h"

#ifndef lint
static const char sccsid[] = "@(#)log_get.c	10.38 (Sleepycat) 10/3/98";
#endif /* not lint */

#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>

#include <errno.h>
#include <string.h>
#include <unistd.h>
#endif

#include "db_int.h"
#include "shqueue.h"
#include "db_page.h"
#include "log.h"
#include "hash.h"
#include "common_ext.h"

/*
 * log_get --
 *	Get a log record.
 */
int
log_get(dblp, alsn, dbt, flags)
	DB_LOG *dblp;
	DB_LSN *alsn;
	DBT *dbt;
	u_int32_t flags;
{
	int ret;

	LOG_PANIC_CHECK(dblp);

	/* Validate arguments. */
	if (flags != DB_CHECKPOINT && flags != DB_CURRENT &&
	    flags != DB_FIRST && flags != DB_LAST &&
	    flags != DB_NEXT && flags != DB_PREV && flags != DB_SET)
		return (__db_ferr(dblp->dbenv, "log_get", 1));

	if (F_ISSET(dblp, DB_AM_THREAD)) {
		if (flags == DB_NEXT || flags == DB_PREV || flags == DB_CURRENT)
			return (__db_ferr(dblp->dbenv, "log_get", 1));
		if (!F_ISSET(dbt, DB_DBT_USERMEM | DB_DBT_MALLOC))
			return (__db_ferr(dblp->dbenv, "threaded data", 1));
	}

	LOCK_LOGREGION(dblp);

	/*
	 * If we get one of the log's header records, repeat the operation.
	 * This assumes that applications don't ever request the log header
	 * records by LSN, but that seems reasonable to me.
	 */
	ret = __log_get(dblp, alsn, dbt, flags, 0);
	if (ret == 0 && alsn->offset == 0) {
		switch (flags) {
		case DB_FIRST:
			flags = DB_NEXT;
			break;
		case DB_LAST:
			flags = DB_PREV;
			break;
		}
		ret = __log_get(dblp, alsn, dbt, flags, 0);
	}

	UNLOCK_LOGREGION(dblp);

	return (ret);
}

/*
 * __log_get --
 *	Get a log record; internal version.
 *
 * PUBLIC: int __log_get __P((DB_LOG *, DB_LSN *, DBT *, u_int32_t, int));
 */
int
__log_get(dblp, alsn, dbt, flags, silent)
	DB_LOG *dblp;
	DB_LSN *alsn;
	DBT *dbt;
	u_int32_t flags;
	int silent;
{
	DB_LSN nlsn;
	HDR hdr;
	LOG *lp;
	size_t len;
	ssize_t nr;
	int cnt, ret;
	char *np, *tbuf;
	const char *fail;
	void *p, *shortp;

	lp = dblp->lp;
	fail = np = tbuf = NULL;

	nlsn = dblp->c_lsn;
	switch (flags) {
	case DB_CHECKPOINT:
		nlsn = lp->chkpt_lsn;
		if (IS_ZERO_LSN(nlsn)) {
			__db_err(dblp->dbenv,
	"log_get: unable to find checkpoint record: no checkpoint set.");
			ret = ENOENT;
			goto err2;
		}
		break;
	case DB_NEXT:				/* Next log record. */
		if (!IS_ZERO_LSN(nlsn)) {
			/* Increment the cursor by the cursor record size. */
			nlsn.offset += dblp->c_len;
			break;
		}
		/* FALLTHROUGH */
	case DB_FIRST:				/* Find the first log record. */
		/* Find the first log file. */
		if ((ret = __log_find(dblp, 1, &cnt)) != 0)
			goto err2;

		/*
		 * We may have only entered records in the buffer, and not
		 * yet written a log file.  If no log files were found and
		 * there's anything in the buffer, it belongs to file 1.
		 */
		if (cnt == 0)
			cnt = 1;

		nlsn.file = cnt;
		nlsn.offset = 0;
		break;
	case DB_CURRENT:			/* Current log record. */
		break;
	case DB_PREV:				/* Previous log record. */
		if (!IS_ZERO_LSN(nlsn)) {
			/* If at start-of-file, move to the previous file. */
			if (nlsn.offset == 0) {
				if (nlsn.file == 1 ||
				    __log_valid(dblp, nlsn.file - 1, 0) != 0)
					return (DB_NOTFOUND);

				--nlsn.file;
				nlsn.offset = dblp->c_off;
			} else
				nlsn.offset = dblp->c_off;
			break;
		}
		/* FALLTHROUGH */
	case DB_LAST:				/* Last log record. */
		nlsn.file = lp->lsn.file;
		nlsn.offset = lp->lsn.offset - lp->len;
		break;
	case DB_SET:				/* Set log record. */
		nlsn = *alsn;
		break;
	}

retry:
	/* Return 1 if the request is past end-of-file. */
	if (nlsn.file > lp->lsn.file ||
	    (nlsn.file == lp->lsn.file && nlsn.offset >= lp->lsn.offset))
		return (DB_NOTFOUND);

	/* If we've switched files, discard the current fd. */
	if (dblp->c_lsn.file != nlsn.file && dblp->c_fd != -1) {
		(void)__os_close(dblp->c_fd);
		dblp->c_fd = -1;
	}

	/* If the entire record is in the in-memory buffer, copy it out. */
	if (nlsn.file == lp->lsn.file && nlsn.offset >= lp->w_off) {
		/* Copy the header. */
		p = lp->buf + (nlsn.offset - lp->w_off);
		memcpy(&hdr, p, sizeof(HDR));

		/* Copy the record. */
		len = hdr.len - sizeof(HDR);
		if ((ret = __db_retcopy(dbt, (u_int8_t *)p + sizeof(HDR),
		    len, &dblp->c_dbt.data, &dblp->c_dbt.ulen, NULL)) != 0)
			goto err1;
		goto cksum;
	}

	/* Acquire a file descriptor. */
	if (dblp->c_fd == -1) {
		if ((ret = __log_name(dblp, nlsn.file,
		    &np, &dblp->c_fd, DB_RDONLY | DB_SEQUENTIAL)) != 0) {
			fail = np;
			goto err1;
		}
		__os_freestr(np);
		np = NULL;
	}

	/* Seek to the header offset and read the header. */
	if ((ret =
	    __os_seek(dblp->c_fd, 0, 0, nlsn.offset, 0, SEEK_SET)) != 0) {
		fail = "seek";
		goto err1;
	}
	if ((ret = __os_read(dblp->c_fd, &hdr, sizeof(HDR), &nr)) != 0) {
		fail = "read";
		goto err1;
	}
	if (nr == sizeof(HDR))
		shortp = NULL;
	else {
		/* If read returns EOF, try the next file. */
		if (nr == 0) {
			if (flags != DB_NEXT || nlsn.file == lp->lsn.file)
				goto corrupt;

			/* Move to the next file. */
			++nlsn.file;
			nlsn.offset = 0;
			goto retry;
		}

		/*
		 * If read returns a short count the rest of the record has
		 * to be in the in-memory buffer.
		 */
		if (lp->b_off < sizeof(HDR) - nr)
			goto corrupt;

		/* Get the rest of the header from the in-memory buffer. */
		memcpy((u_int8_t *)&hdr + nr, lp->buf, sizeof(HDR) - nr);
		shortp = lp->buf + (sizeof(HDR) - nr);
	}

	/*
	 * Check for buffers of 0's, that's what we usually see during
	 * recovery, although it's certainly not something on which we
	 * can depend.
	 */
	if (hdr.len <= sizeof(HDR))
		goto corrupt;
	len = hdr.len - sizeof(HDR);

	/* If we've already moved to the in-memory buffer, fill from there. */
	if (shortp != NULL) {
		if (lp->b_off < ((u_int8_t *)shortp - lp->buf) + len)
			goto corrupt;
		if ((ret = __db_retcopy(dbt, shortp, len,
		    &dblp->c_dbt.data, &dblp->c_dbt.ulen, NULL)) != 0)
			goto err1;
		goto cksum;
	}

	/*
	 * Allocate temporary memory to hold the record.
	 *
	 * XXX
	 * We're calling malloc(3) with a region locked.  This isn't
	 * a good idea.
	 */
	if ((ret = __os_malloc(len, NULL, &tbuf)) != 0)
		goto err1;

	/*
	 * Read the record into the buffer.  If read returns a short count,
	 * there was an error or the rest of the record is in the in-memory
	 * buffer.  Note, the information may be garbage if we're in recovery,
	 * so don't read past the end of the buffer's memory.
	 */
	if ((ret = __os_read(dblp->c_fd, tbuf, len, &nr)) != 0) {
		fail = "read";
		goto err1;
	}
	if (len - nr > sizeof(lp->buf))
		goto corrupt;
	if (nr != (ssize_t)len) {
		if (lp->b_off < len - nr)
			goto corrupt;

		/* Get the rest of the record from the in-memory buffer. */
		memcpy((u_int8_t *)tbuf + nr, lp->buf, len - nr);
	}

	/* Copy the record into the user's DBT. */
	if ((ret = __db_retcopy(dbt, tbuf, len,
	    &dblp->c_dbt.data, &dblp->c_dbt.ulen, NULL)) != 0)
		goto err1;
	__os_free(tbuf, 0);
	tbuf = NULL;

cksum:	if (hdr.cksum != __ham_func4(dbt->data, dbt->size)) {
		if (!silent)
			__db_err(dblp->dbenv, "log_get: checksum mismatch");
		goto corrupt;
	}

	/* Update the cursor and the return lsn. */
	dblp->c_off = hdr.prev;
	dblp->c_len = hdr.len;
	dblp->c_lsn = *alsn = nlsn;

	return (0);

corrupt:/*
	 * This is the catchall -- for some reason we didn't find enough
	 * information or it wasn't reasonable information, and it wasn't
	 * because a system call failed.
	 */
	ret = EIO;
	fail = "read";

err1:	if (!silent) {
		if (fail == NULL)
			__db_err(dblp->dbenv, "log_get: %s", strerror(ret));
		else
			__db_err(dblp->dbenv,
			    "log_get: %s: %s", fail, strerror(ret));
	}
err2:	if (np != NULL)
		__os_freestr(np);
	if (tbuf != NULL)
		__os_free(tbuf, 0);
	return (ret);
}