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137 lines
4.2 KiB
137 lines
4.2 KiB
/*-
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* See the file LICENSE for redistribution information.
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*
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* Copyright (c) 1996, 1997, 1998, 1999
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* Sleepycat Software. All rights reserved.
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*/
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#include "db_config.h"
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#ifndef lint
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static const char sccsid[] = "@(#)log_findckp.c 11.1 (Sleepycat) 7/24/99";
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#endif /* not lint */
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#ifndef NO_SYSTEM_INCLUDES
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#include <sys/types.h>
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#include <errno.h>
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#include <string.h>
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#endif
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#include "db_int.h"
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#include "log.h"
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#include "txn.h"
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/*
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* CDB___log_findckp --
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*
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* Looks for the most recent checkpoint that occurs before the most recent
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* checkpoint LSN, subject to the constraint that there must be at least two
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* checkpoints. The reason you need two checkpoints is that you might have
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* crashed during the most recent one and may not have a copy of all the
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* open files. This is the point from which recovery can start and the
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* point up to which archival/truncation can take place. Checkpoints in
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* the log look like:
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*
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* -------------------------------------------------------------------
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* | ckp A, ckplsn 100 | .... record .... | ckp B, ckplsn 600 | ...
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* -------------------------------------------------------------------
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* LSN 500 LSN 1000
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*
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* If we read what log returns from using the DB_CKP parameter to logput,
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* we'll get the record at LSN 1000. The checkpoint LSN there is 600.
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* Now we have to scan backwards looking for a checkpoint before LSN 600.
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* We find one at 500. This means that we can truncate the log before
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* 500 or run recovery beginning at 500.
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*
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* Returns 0 if we find a suitable checkpoint or we retrieved the first
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* record in the log from which to start. Returns DB_NOTFOUND if there
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* are no log records, errno on error.
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*
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* PUBLIC: int CDB___log_findckp __P((DB_ENV *, DB_LSN *));
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*/
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int
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CDB___log_findckp(dbenv, lsnp)
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DB_ENV *dbenv;
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DB_LSN *lsnp;
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{
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DBT data;
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DB_LSN ckp_lsn, final_ckp, last_ckp, next_lsn;
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__txn_ckp_args *ckp_args;
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int ret;
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/*
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* Need to find the appropriate point from which to begin
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* recovery.
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*/
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memset(&data, 0, sizeof(data));
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if (F_ISSET(dbenv, DB_ENV_THREAD))
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F_SET(&data, DB_DBT_MALLOC);
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ZERO_LSN(ckp_lsn);
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if ((ret = CDB_log_get(dbenv, &last_ckp, &data, DB_CHECKPOINT)) != 0) {
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if (ret == ENOENT)
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goto get_first;
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else
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return (ret);
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}
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final_ckp = last_ckp;
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next_lsn = last_ckp;
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do {
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if (F_ISSET(dbenv, DB_ENV_THREAD))
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CDB___os_free(data.data, data.size);
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if ((ret = CDB_log_get(dbenv, &next_lsn, &data, DB_SET)) != 0)
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return (ret);
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if ((ret = CDB___txn_ckp_read(data.data, &ckp_args)) != 0) {
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if (F_ISSET(dbenv, DB_ENV_THREAD))
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CDB___os_free(data.data, data.size);
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return (ret);
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}
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if (IS_ZERO_LSN(ckp_lsn))
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ckp_lsn = ckp_args->ckp_lsn;
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if (FLD_ISSET(dbenv->verbose, DB_VERB_CHKPOINT)) {
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CDB___db_err(dbenv, "Checkpoint at: [%lu][%lu]",
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(u_long)last_ckp.file, (u_long)last_ckp.offset);
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CDB___db_err(dbenv, "Checkpoint LSN: [%lu][%lu]",
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(u_long)ckp_args->ckp_lsn.file,
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(u_long)ckp_args->ckp_lsn.offset);
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CDB___db_err(dbenv, "Previous checkpoint: [%lu][%lu]",
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(u_long)ckp_args->last_ckp.file,
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(u_long)ckp_args->last_ckp.offset);
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}
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last_ckp = next_lsn;
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next_lsn = ckp_args->last_ckp;
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CDB___os_free(ckp_args, sizeof(*ckp_args));
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/*
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* Keep looping until either you 1) run out of checkpoints,
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* 2) you've found a checkpoint before the most recent
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* checkpoint's LSN and you have at least 2 checkpoints.
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*/
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} while (!IS_ZERO_LSN(next_lsn) &&
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(CDB_log_compare(&last_ckp, &ckp_lsn) > 0 ||
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CDB_log_compare(&final_ckp, &last_ckp) == 0));
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if (F_ISSET(dbenv, DB_ENV_THREAD))
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CDB___os_free(data.data, data.size);
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/*
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* At this point, either, next_lsn is ZERO or ckp_lsn is the
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* checkpoint lsn and last_ckp is the LSN of the last checkpoint
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* before ckp_lsn. If the compare in the loop is still true, then
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* next_lsn must be 0 and we need to roll forward from the
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* beginning of the log.
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*/
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if (CDB_log_compare(&last_ckp, &ckp_lsn) >= 0 ||
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CDB_log_compare(&final_ckp, &last_ckp) == 0) {
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get_first: if ((ret = CDB_log_get(dbenv, &last_ckp, &data, DB_FIRST)) != 0)
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return (ret);
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if (F_ISSET(dbenv, DB_ENV_THREAD))
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CDB___os_free(data.data, data.size);
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}
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*lsnp = last_ckp;
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return (IS_ZERO_LSN(last_ckp) ? DB_NOTFOUND : 0);
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}
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