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/*-
* 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_findckp.c 10.17 (Sleepycat) 9/17/98";
#endif /* not lint */
#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>
#include <errno.h>
#include <string.h>
#endif
#include "db_int.h"
#include "shqueue.h"
#include "log.h"
#include "txn.h"
#include "common_ext.h"
/*
* __log_findckp --
*
* Looks for the most recent checkpoint that occurs before the most recent
* checkpoint LSN, subject to the constraint that there must be at least two
* checkpoints. The reason you need two checkpoints is that you might have
* crashed during the most recent one and may not have a copy of all the
* open files. This is the point from which recovery can start and the
* point up to which archival/truncation can take place. Checkpoints in
* the log look like:
*
* -------------------------------------------------------------------
* | ckp A, ckplsn 100 | .... record .... | ckp B, ckplsn 600 | ...
* -------------------------------------------------------------------
* LSN 500 LSN 1000
*
* If we read what log returns from using the DB_CKP parameter to logput,
* we'll get the record at LSN 1000. The checkpoint LSN there is 600.
* Now we have to scan backwards looking for a checkpoint before LSN 600.
* We find one at 500. This means that we can truncate the log before
* 500 or run recovery beginning at 500.
*
* Returns 0 if we find a suitable checkpoint or we retrieved the
* first record in the log from which to start.
* Returns DB_NOTFOUND if there are no log records.
* Returns errno on error.
*
* PUBLIC: int __log_findckp __P((DB_LOG *, DB_LSN *));
*/
int
__log_findckp(lp, lsnp)
DB_LOG *lp;
DB_LSN *lsnp;
{
DBT data;
DB_LSN ckp_lsn, final_ckp, last_ckp, next_lsn;
__txn_ckp_args *ckp_args;
int ret, verbose;
verbose = lp->dbenv != NULL && lp->dbenv->db_verbose != 0;
/*
* Need to find the appropriate point from which to begin
* recovery.
*/
memset(&data, 0, sizeof(data));
if (F_ISSET(lp, DB_AM_THREAD))
F_SET(&data, DB_DBT_MALLOC);
ZERO_LSN(ckp_lsn);
if ((ret = log_get(lp, &last_ckp, &data, DB_CHECKPOINT)) != 0) {
if (ret == ENOENT)
goto get_first;
else
return (ret);
}
final_ckp = last_ckp;
next_lsn = last_ckp;
do {
if (F_ISSET(lp, DB_AM_THREAD))
__os_free(data.data, data.size);
if ((ret = log_get(lp, &next_lsn, &data, DB_SET)) != 0)
return (ret);
if ((ret = __txn_ckp_read(data.data, &ckp_args)) != 0) {
if (F_ISSET(lp, DB_AM_THREAD))
__os_free(data.data, data.size);
return (ret);
}
if (IS_ZERO_LSN(ckp_lsn))
ckp_lsn = ckp_args->ckp_lsn;
if (verbose) {
__db_err(lp->dbenv, "Checkpoint at: [%lu][%lu]",
(u_long)last_ckp.file, (u_long)last_ckp.offset);
__db_err(lp->dbenv, "Checkpoint LSN: [%lu][%lu]",
(u_long)ckp_args->ckp_lsn.file,
(u_long)ckp_args->ckp_lsn.offset);
__db_err(lp->dbenv, "Previous checkpoint: [%lu][%lu]",
(u_long)ckp_args->last_ckp.file,
(u_long)ckp_args->last_ckp.offset);
}
last_ckp = next_lsn;
next_lsn = ckp_args->last_ckp;
__os_free(ckp_args, sizeof(*ckp_args));
/*
* Keep looping until either you 1) run out of checkpoints,
* 2) you've found a checkpoint before the most recent
* checkpoint's LSN and you have at least 2 checkpoints.
*/
} while (!IS_ZERO_LSN(next_lsn) &&
(log_compare(&last_ckp, &ckp_lsn) > 0 ||
log_compare(&final_ckp, &last_ckp) == 0));
if (F_ISSET(lp, DB_AM_THREAD))
__os_free(data.data, data.size);
/*
* At this point, either, next_lsn is ZERO or ckp_lsn is the
* checkpoint lsn and last_ckp is the LSN of the last checkpoint
* before ckp_lsn. If the compare in the loop is still true, then
* next_lsn must be 0 and we need to roll forward from the
* beginning of the log.
*/
if (log_compare(&last_ckp, &ckp_lsn) > 0 ||
log_compare(&final_ckp, &last_ckp) == 0) {
get_first: if ((ret = log_get(lp, &last_ckp, &data, DB_FIRST)) != 0)
return (ret);
if (F_ISSET(lp, DB_AM_THREAD))
__os_free(data.data, data.size);
}
*lsnp = last_ckp;
return (IS_ZERO_LSN(last_ckp) ? DB_NOTFOUND : 0);
}
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