/*- * 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 10.15 (Sleepycat) 4/26/98"; #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. 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, 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); } next_lsn = last_ckp; do { if (F_ISSET(lp, DB_AM_THREAD)) __db_free(data.data); 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)) __db_free(data.data); 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; __db_free(ckp_args); } while (!IS_ZERO_LSN(next_lsn) && log_compare(&last_ckp, &ckp_lsn) > 0); if (F_ISSET(lp, DB_AM_THREAD)) __db_free(data.data); /* * 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) { get_first: if ((ret = log_get(lp, &last_ckp, &data, DB_FIRST)) != 0) return (ret); if (F_ISSET(lp, DB_AM_THREAD)) __db_free(data.data); } *lsnp = last_ckp; return (IS_ZERO_LSN(last_ckp) ? DB_NOTFOUND : 0); }