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log.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996,2007 Oracle.  All rights reserved.
 *
 * $Id: log.c,v 12.54 2007/06/04 21:30:51 sue Exp $
 */

#include "db_config.h"

#include "db_int.h"
#include "dbinc/crypto.h"
#include "dbinc/hmac.h"
#include "dbinc/log.h"
#include "dbinc/txn.h"

static int  __log_init __P((DB_ENV *, DB_LOG *));
static int  __log_recover __P((DB_LOG *));
static size_t     __log_region_size __P((DB_ENV *));

/*
 * __log_open --
 *    Internal version of log_open: only called from DB_ENV->open.
 *
 * PUBLIC: int __log_open __P((DB_ENV *, int));
 */
int
__log_open(dbenv, create_ok)
      DB_ENV *dbenv;
      int create_ok;
{
      DB_LOG *dblp;
      LOG *lp;
      u_int8_t *bulk;
      int region_locked, ret;

      region_locked = 0;

      /* Create/initialize the DB_LOG structure. */
      if ((ret = __os_calloc(dbenv, 1, sizeof(DB_LOG), &dblp)) != 0)
            return (ret);
      dblp->dbenv = dbenv;

      /* Set the default buffer size, if not otherwise configured. */
      if (dbenv->lg_bsize == 0)
            dbenv->lg_bsize = F_ISSET(dbenv, DB_ENV_LOG_INMEMORY) ?
                LG_BSIZE_INMEM : LG_BSIZE_DEFAULT;

      /* Join/create the log region. */
      dblp->reginfo.dbenv = dbenv;
      dblp->reginfo.type = REGION_TYPE_LOG;
      dblp->reginfo.id = INVALID_REGION_ID;
      dblp->reginfo.flags = REGION_JOIN_OK;
      if (create_ok)
            F_SET(&dblp->reginfo, REGION_CREATE_OK);
      if ((ret = __env_region_attach(
          dbenv, &dblp->reginfo, __log_region_size(dbenv))) != 0)
            goto err;

      /* If we created the region, initialize it. */
      if (F_ISSET(&dblp->reginfo, REGION_CREATE))
            if ((ret = __log_init(dbenv, dblp)) != 0)
                  goto err;

      /* Set the local addresses. */
      lp = dblp->reginfo.primary =
          R_ADDR(&dblp->reginfo, dblp->reginfo.rp->primary);
      dblp->bufp = R_ADDR(&dblp->reginfo, lp->buffer_off);

      /*
       * If the region is threaded, we have to lock the DBREG list, and we
       * need to allocate a mutex for that purpose.
       */
      if ((ret = __mutex_alloc(dbenv,
          MTX_LOG_REGION, DB_MUTEX_PROCESS_ONLY, &dblp->mtx_dbreg)) != 0)
            goto err;

      /*
       * Set the handle -- we may be about to run recovery, which allocates
       * log cursors.  Log cursors require logging be already configured,
       * and the handle being set is what demonstrates that.
       *
       * If we created the region, run recovery.  If that fails, make sure
       * we reset the log handle before cleaning up, otherwise we will try
       * and clean up again in the mainline DB_ENV initialization code.
       */
      dbenv->lg_handle = dblp;

      if (F_ISSET(&dblp->reginfo, REGION_CREATE)) {
            /*
             * We first take the log file size from the environment, if
             * specified.  If that wasn't set, default it.  Regardless,
             * recovery may set it from the persistent information in a
             * log file header.
             */
            if (lp->log_size == 0)
                  lp->log_size = F_ISSET(dbenv, DB_ENV_LOG_INMEMORY) ?
                      LG_MAX_INMEM : LG_MAX_DEFAULT;

            if ((ret = __log_recover(dblp)) != 0)
                  goto err;

            /*
             * If the next log file size hasn't been set yet, default it
             * to the current log file size.
             */
            if (lp->log_nsize == 0)
                  lp->log_nsize = lp->log_size;

            /*
             * If we haven't written any log files, write the first one
             * so that checkpoint gets a valid ckp_lsn value.
             */
            if (IS_INIT_LSN(lp->lsn) &&
                (ret = __log_newfile(dblp, NULL, 0, 0)) != 0)
                  goto err;

            /*
             * Initialize replication's next-expected LSN value
             * and replication's bulk buffer.
             */
            lp->ready_lsn = lp->lsn;
            if (IS_ENV_REPLICATED(dbenv)) {
                  if ((ret =
                      __env_alloc(&dblp->reginfo, MEGABYTE, &bulk)) != 0)
                        goto err;
                  lp->bulk_buf = R_OFFSET(&dblp->reginfo, bulk);
                  lp->bulk_len = MEGABYTE;
                  lp->bulk_off = 0;
            } else {
                  lp->bulk_buf = INVALID_ROFF;
                  lp->bulk_len = 0;
                  lp->bulk_off = 0;
            }
      } else {
            /*
             * A process joining the region may have reset the log file
             * size, too.  If so, it only affects the next log file we
             * create.  We need to check that the size is reasonable given
             * the buffer size in the region.
             */
            LOG_SYSTEM_LOCK(dbenv);
            region_locked = 1;

             if (dbenv->lg_size != 0) {
                  if ((ret =
                      __log_check_sizes(dbenv, dbenv->lg_size, 0)) != 0)
                        goto err;

                  lp->log_nsize = dbenv->lg_size;
             }

            /* Migrate persistent flags from the region into the DB_ENV. */
            if (lp->db_log_autoremove)
                  F_SET(dbenv, DB_ENV_LOG_AUTOREMOVE);
            if (lp->db_log_inmemory)
                  F_SET(dbenv, DB_ENV_LOG_INMEMORY);

            LOG_SYSTEM_UNLOCK(dbenv);
            region_locked = 0;
      }

      return (0);

err:  dbenv->lg_handle = NULL;
      if (dblp->reginfo.addr != NULL) {
            if (region_locked)
                  LOG_SYSTEM_UNLOCK(dbenv);
            (void)__env_region_detach(dbenv, &dblp->reginfo, 0);
      }

      (void)__mutex_free(dbenv, &dblp->mtx_dbreg);
      __os_free(dbenv, dblp);

      return (ret);
}

/*
 * __log_init --
 *    Initialize a log region in shared memory.
 */
static int
__log_init(dbenv, dblp)
      DB_ENV *dbenv;
      DB_LOG *dblp;
{
      LOG *lp;
      int ret;
      void *p;

      /*
       * This is the first point where we can validate the buffer size,
       * because we know all three settings have been configured (file size,
       * buffer size and the in-memory flag).
       */
      if ((ret =
         __log_check_sizes(dbenv, dbenv->lg_size, dbenv->lg_bsize)) != 0)
            return (ret);

      if ((ret = __env_alloc(&dblp->reginfo,
          sizeof(*lp), &dblp->reginfo.primary)) != 0)
            goto mem_err;
      dblp->reginfo.rp->primary =
          R_OFFSET(&dblp->reginfo, dblp->reginfo.primary);
      lp = dblp->reginfo.primary;
      memset(lp, 0, sizeof(*lp));

      if ((ret =
          __mutex_alloc(dbenv, MTX_LOG_REGION, 0, &lp->mtx_region)) != 0)
            return (ret);

      lp->fid_max = 0;
      SH_TAILQ_INIT(&lp->fq);
      lp->free_fid_stack = INVALID_ROFF;
      lp->free_fids = lp->free_fids_alloced = 0;

      /* Initialize LOG LSNs. */
      INIT_LSN(lp->lsn);
      INIT_LSN(lp->t_lsn);

      /*
       * It's possible to be waiting for an LSN of [1][0], if a replication
       * client gets the first log record out of order.  An LSN of [0][0]
       * signifies that we're not waiting.
       */
      ZERO_LSN(lp->waiting_lsn);

      /*
       * Log makes note of the fact that it ran into a checkpoint on
       * startup if it did so, as a recovery optimization.  A zero
       * LSN signifies that it hasn't found one [yet].
       */
      ZERO_LSN(lp->cached_ckp_lsn);

      if ((ret =
          __mutex_alloc(dbenv, MTX_LOG_FILENAME, 0, &lp->mtx_filelist)) != 0)
            return (ret);
      if ((ret = __mutex_alloc(dbenv, MTX_LOG_FLUSH, 0, &lp->mtx_flush)) != 0)
            return (ret);

      /* Initialize the buffer. */
      if ((ret = __env_alloc(&dblp->reginfo, dbenv->lg_bsize, &p)) != 0) {
mem_err:    __db_errx( dbenv, "unable to allocate log region memory");
            return (ret);
      }
      lp->regionmax = dbenv->lg_regionmax;
      lp->buffer_off = R_OFFSET(&dblp->reginfo, p);
      lp->buffer_size = dbenv->lg_bsize;
      lp->filemode = dbenv->lg_filemode;
      lp->log_size = lp->log_nsize = dbenv->lg_size;

      /* Initialize the commit Queue. */
      SH_TAILQ_INIT(&lp->free_commits);
      SH_TAILQ_INIT(&lp->commits);
      lp->ncommit = 0;

      /* Initialize the logfiles list for in-memory logs. */
      SH_TAILQ_INIT(&lp->logfiles);
      SH_TAILQ_INIT(&lp->free_logfiles);

      /*
       * Fill in the log's persistent header.  Don't fill in the log file
       * sizes, as they may change at any time and so have to be filled in
       * as each log file is created.
       */
      lp->persist.magic = DB_LOGMAGIC;
      /*
       * Don't use __log_set_version because dbenv->dblp isn't set up yet.
       */
      lp->persist.version = DB_LOGVERSION;
      lp->persist.notused = 0;

      /* Migrate persistent flags from the DB_ENV into the region. */
      if (F_ISSET(dbenv, DB_ENV_LOG_AUTOREMOVE))
            lp->db_log_autoremove = 1;
      if (F_ISSET(dbenv, DB_ENV_LOG_INMEMORY))
            lp->db_log_inmemory = 1;

      (void)time(&lp->timestamp);
      return (0);
}

/*
 * __log_recover --
 *    Recover a log.
 */
static int
__log_recover(dblp)
      DB_LOG *dblp;
{
      DBT dbt;
      DB_ENV *dbenv;
      DB_LOGC *logc;
      DB_LSN lsn;
      LOG *lp;
      u_int32_t cnt, rectype;
      int ret;
      logfile_validity status;

      logc = NULL;
      dbenv = dblp->dbenv;
      lp = dblp->reginfo.primary;

      /*
       * Find a log file.  If none exist, we simply return, leaving
       * everything initialized to a new log.
       */
      if ((ret = __log_find(dblp, 0, &cnt, &status)) != 0)
            return (ret);
      if (cnt == 0)
            return (0);

      /*
       * If the last file is an old, unreadable version, start a new
       * file.  Don't bother finding the end of the last log file;
       * we assume that it's valid in its entirety, since the user
       * should have shut down cleanly or run recovery before upgrading.
       */
      if (status == DB_LV_OLD_UNREADABLE) {
            lp->lsn.file = lp->s_lsn.file = cnt + 1;
            lp->lsn.offset = lp->s_lsn.offset = 0;
            goto skipsearch;
      }
      DB_ASSERT(dbenv,
          (status == DB_LV_NORMAL || status == DB_LV_OLD_READABLE));

      /*
       * We have the last useful log file and we've loaded any persistent
       * information.  Set the end point of the log past the end of the last
       * file. Read the last file, looking for the last checkpoint and
       * the log's end.
       */
      lp->lsn.file = cnt + 1;
      lp->lsn.offset = 0;
      lsn.file = cnt;
      lsn.offset = 0;

      /*
       * Allocate a cursor and set it to the first record.  This shouldn't
       * fail, leave error messages on.
       */
      if ((ret = __log_cursor(dbenv, &logc)) != 0)
            return (ret);
      F_SET(logc, DB_LOG_LOCKED);
      memset(&dbt, 0, sizeof(dbt));
      if ((ret = __logc_get(logc, &lsn, &dbt, DB_SET)) != 0)
            goto err;

      /*
       * Read to the end of the file.  This may fail at some point, so
       * turn off error messages.
       */
      F_SET(logc, DB_LOG_SILENT_ERR);
      while (__logc_get(logc, &lsn, &dbt, DB_NEXT) == 0) {
            if (dbt.size < sizeof(u_int32_t))
                  continue;
            memcpy(&rectype, dbt.data, sizeof(u_int32_t));
            if (rectype == DB___txn_ckp)
                  /*
                   * If we happen to run into a checkpoint, cache its
                   * LSN so that the transaction system doesn't have
                   * to walk this log file again looking for it.
                   */
                  lp->cached_ckp_lsn = lsn;
      }
      F_CLR(logc, DB_LOG_SILENT_ERR);

      /*
       * We now know where the end of the log is.  Set the first LSN that
       * we want to return to an application and the LSN of the last known
       * record on disk.
       */
      lp->lsn = lsn;
      lp->s_lsn = lsn;
      lp->lsn.offset += logc->len;
      lp->s_lsn.offset += logc->len;

      /* Set up the current buffer information, too. */
      lp->len = logc->len;
      lp->a_off = 0;
      lp->b_off = 0;
      lp->w_off = lp->lsn.offset;

skipsearch:
      if (FLD_ISSET(dbenv->verbose, DB_VERB_RECOVERY))
            __db_msg(dbenv,
                "Finding last valid log LSN: file: %lu offset %lu",
                (u_long)lp->lsn.file, (u_long)lp->lsn.offset);

err:  if (logc != NULL)
            (void)__logc_close(logc);

      return (ret);
}

/*
 * __log_find --
 *    Try to find a log file.  If find_first is set, valp will contain
 * the number of the first readable log file, else it will contain the number
 * of the last log file (which may be too old to read).
 *
 * PUBLIC: int __log_find __P((DB_LOG *, int, u_int32_t *, logfile_validity *));
 */
int
__log_find(dblp, find_first, valp, statusp)
      DB_LOG *dblp;
      int find_first;
      u_int32_t *valp;
      logfile_validity *statusp;
{
      DB_ENV *dbenv;
      LOG *lp;
      logfile_validity logval_status, status;
      struct __db_filestart *filestart;
      u_int32_t clv, logval;
      int cnt, fcnt, ret;
      const char *dir;
      char *c, **names, *p, *q;

      dbenv = dblp->dbenv;
      lp = dblp->reginfo.primary;
      logval_status = status = DB_LV_NONEXISTENT;

      /* Return a value of 0 as the log file number on failure. */
      *valp = 0;

      if (lp->db_log_inmemory) {
            filestart = find_first ?
                SH_TAILQ_FIRST(&lp->logfiles, __db_filestart) :
                SH_TAILQ_LAST(&lp->logfiles, links, __db_filestart);
            if (filestart != NULL) {
                  *valp = filestart->file;
                  logval_status = DB_LV_NORMAL;
            }
            *statusp = logval_status;
            return (0);
      }

      /* Find the directory name. */
      if ((ret = __log_name(dblp, 1, &p, NULL, 0)) != 0)
            return (ret);
      if ((q = __db_rpath(p)) == NULL)
            dir = PATH_DOT;
      else {
            *q = '\0';
            dir = p;
      }

      /* Get the list of file names. */
      if ((ret = __os_dirlist(dbenv, dir, &names, &fcnt)) != 0) {
            __db_err(dbenv, ret, "%s", dir);
            __os_free(dbenv, p);
            return (ret);
      }

      /* Search for a valid log file name. */
      for (cnt = fcnt, clv = logval = 0; --cnt >= 0;) {
            if (strncmp(names[cnt], LFPREFIX, sizeof(LFPREFIX) - 1) != 0)
                  continue;

            /*
             * Names of the form log\.[0-9]* are reserved for DB.  Other
             * names sharing LFPREFIX, such as "log.db", are legal.
             */
            for (c = names[cnt] + sizeof(LFPREFIX) - 1; *c != '\0'; c++)
                  if (!isdigit((int)*c))
                        break;
            if (*c != '\0')
                  continue;

            /*
             * Use atol, not atoi; if an "int" is 16-bits, the largest
             * log file name won't fit.
             */
            clv = (u_int32_t)atol(names[cnt] + (sizeof(LFPREFIX) - 1));

            /*
             * If searching for the first log file, we want to return the
             * oldest log file we can read, or, if no readable log files
             * exist, the newest log file we can't read (the crossover
             * point between the old and new versions of the log file).
             *
             * If we're searching for the last log file, we want to return
             * the newest log file, period.
             *
             * Readable log files should never precede unreadable log
             * files, that would mean the admin seriously screwed up.
             */
            if (find_first) {
                  if (logval != 0 &&
                      status != DB_LV_OLD_UNREADABLE && clv > logval)
                        continue;
            } else
                  if (logval != 0 && clv < logval)
                        continue;

            if ((ret = __log_valid(dblp, clv, 1, NULL, 0,
                &status, NULL)) != 0) {
                  __db_err(
                      dbenv, ret, "Invalid log file: %s", names[cnt]);
                  goto err;
            }
            switch (status) {
            case DB_LV_NONEXISTENT:
                  /* __log_valid never returns DB_LV_NONEXISTENT. */
                  DB_ASSERT(dbenv, 0);
                  break;
            case DB_LV_INCOMPLETE:
                  /*
                   * The last log file may not have been initialized --
                   * it's possible to create a log file but not write
                   * anything to it.  If performing recovery (that is,
                   * if find_first isn't set), ignore the file, it's
                   * not interesting.  If we're searching for the first
                   * log record, return the file (assuming we don't find
                   * something better), as the "real" first log record
                   * is likely to be in the log buffer, and we want to
                   * set the file LSN for our return.
                   */
                  if (find_first)
                        goto found;
                  break;
            case DB_LV_OLD_UNREADABLE:
                  /*
                   * If we're searching for the first log file, then we
                   * only want this file if we don't yet have a file or
                   * already have an unreadable file and this one is
                   * newer than that one.  If we're searching for the
                   * last log file, we always want this file because we
                   * wouldn't be here if it wasn't newer than our current
                   * choice.
                   */
                  if (!find_first || logval == 0 ||
                      (status == DB_LV_OLD_UNREADABLE && clv > logval))
                        goto found;
                  break;
            case DB_LV_NORMAL:
            case DB_LV_OLD_READABLE:
found:                  logval = clv;
                  logval_status = status;
                  break;
            }
      }

      *valp = logval;

err:  __os_dirfree(dbenv, names, fcnt);
      __os_free(dbenv, p);
      *statusp = logval_status;

      return (ret);
}

/*
 * log_valid --
 *    Validate a log file.  Returns an error code in the event of
 *    a fatal flaw in a the specified log file;  returns success with
 *    a code indicating the currentness and completeness of the specified
 *    log file if it is not unexpectedly flawed (that is, if it's perfectly
 *    normal, if it's zero-length, or if it's an old version).
 *
 * PUBLIC: int __log_valid __P((DB_LOG *, u_int32_t, int,
 * PUBLIC:     DB_FH **, u_int32_t, logfile_validity *, u_int32_t *));
 */
int
__log_valid(dblp, number, set_persist, fhpp, flags, statusp, versionp)
      DB_LOG *dblp;
      u_int32_t number;
      int set_persist;
      DB_FH **fhpp;
      u_int32_t flags;
      logfile_validity *statusp;
      u_int32_t *versionp;
{
      DB_CIPHER *db_cipher;
      DB_ENV *dbenv;
      DB_FH *fhp;
      HDR *hdr;
      LOG *lp;
      LOGP *persist;
      logfile_validity status;
      size_t hdrsize, nr, recsize;
      int is_hmac, ret;
      u_int8_t *tmp;
      char *fname;

      dbenv = dblp->dbenv;
      db_cipher = dbenv->crypto_handle;
      fhp = NULL;
      persist = NULL;
      status = DB_LV_NORMAL;
      tmp = NULL;

      /* Return the file handle to our caller, on request */
      if (fhpp != NULL)
            *fhpp = NULL;

      if (flags == 0)
            flags = DB_OSO_RDONLY | DB_OSO_SEQ;
      /* Try to open the log file. */
      if ((ret = __log_name(dblp, number, &fname, &fhp, flags)) != 0) {
            __os_free(dbenv, fname);
            return (ret);
      }

      hdrsize = HDR_NORMAL_SZ;
      is_hmac = 0;
      recsize = sizeof(LOGP);
      if (CRYPTO_ON(dbenv)) {
            hdrsize = HDR_CRYPTO_SZ;
            recsize = sizeof(LOGP);
            recsize += db_cipher->adj_size(recsize);
            is_hmac = 1;
      }
      if ((ret = __os_calloc(dbenv, 1, recsize + hdrsize, &tmp)) != 0)
            goto err;

      hdr = (HDR *)tmp;
      persist = (LOGP *)(tmp + hdrsize);
      /*
       * Try to read the header.  This can fail if the log is truncated, or
       * if we find a preallocated log file where the header has not yet been
       * written, so we need to check whether the header is zero-filled.
       */
      if ((ret = __os_read(dbenv, fhp, tmp, recsize + hdrsize, &nr)) != 0 ||
          nr != recsize + hdrsize ||
          (hdr->len == 0 && persist->magic == 0 && persist->log_size == 0)) {
            if (ret == 0)
                  status = DB_LV_INCOMPLETE;
            else
                  /*
                   * The error was a fatal read error, not just an
                   * incompletely initialized log file.
                   */
                  __db_err(dbenv, ret, "ignoring log file: %s", fname);
            goto err;
      }

      /*
       * Now we have to validate the persistent record.  We have
       * several scenarios we have to deal with:
       *
       * 1.  User has crypto turned on:
       *    - They're reading an old, unencrypted log file
       *      .  We will fail the record size match check below.
       *    - They're reading a current, unencrypted log file
       *      .  We will fail the record size match check below.
       *    - They're reading an old, encrypted log file [NOT YET]
       *      .  After decryption we'll fail the version check.  [NOT YET]
       *    - They're reading a current, encrypted log file
       *      .  We should proceed as usual.
       * 2.  User has crypto turned off:
       *    - They're reading an old, unencrypted log file
       *      .  We will fail the version check.
       *    - They're reading a current, unencrypted log file
       *      .  We should proceed as usual.
       *    - They're reading an old, encrypted log file [NOT YET]
       *      .  We'll fail the magic number check (it is encrypted).
       *    - They're reading a current, encrypted log file
       *      .  We'll fail the magic number check (it is encrypted).
       */
      if (CRYPTO_ON(dbenv)) {
            /*
             * If we are trying to decrypt an unencrypted log
             * we can only detect that by having an unreasonable
             * data length for our persistent data.
             */
            if ((hdr->len - hdrsize) != sizeof(LOGP)) {
                  __db_errx(dbenv, "log record size mismatch");
                  goto err;
            }
            /* Check the checksum and decrypt. */
            if ((ret = __db_check_chksum(dbenv, hdr, db_cipher,
                &hdr->chksum[0], (u_int8_t *)persist,
                hdr->len - hdrsize, is_hmac)) != 0) {
                  __db_errx(dbenv, "log record checksum mismatch");
                  goto err;
            }
            if ((ret = db_cipher->decrypt(dbenv, db_cipher->data,
                &hdr->iv[0], (u_int8_t *)persist, hdr->len - hdrsize)) != 0)
                  goto err;
      }

      /* Validate the header. */
      if (persist->magic != DB_LOGMAGIC) {
            __db_errx(dbenv,
                "Ignoring log file: %s: magic number %lx, not %lx",
                fname, (u_long)persist->magic, (u_long)DB_LOGMAGIC);
            ret = EINVAL;
            goto err;
      }

      /*
       * Set our status code to indicate whether the log file belongs to an
       * unreadable or readable old version; leave it alone if and only if
       * the log file version is the current one.
       */
      if (persist->version > DB_LOGVERSION) {
            /* This is a fatal error--the log file is newer than DB. */
            __db_errx(dbenv,
                "Unacceptable log file %s: unsupported log version %lu",
                fname, (u_long)persist->version);
            ret = EINVAL;
            goto err;
      } else if (persist->version < DB_LOGOLDVER) {
            status = DB_LV_OLD_UNREADABLE;
            /* This is a non-fatal error, but give some feedback. */
            __db_errx(dbenv,
                "Skipping log file %s: historic log version %lu",
                fname, (u_long)persist->version);
            /*
             * We don't want to set persistent info based on an unreadable
             * region, so jump to "err".
             */
            goto err;
      } else if (persist->version < DB_LOGVERSION)
            status = DB_LV_OLD_READABLE;

      /*
       * Only if we have a current log do we verify the checksum.  We could
       * not check the checksum before checking the magic and version because
       * old log headers put the length and checksum in a different location.
       */
      if (!CRYPTO_ON(dbenv) && ((ret = __db_check_chksum(dbenv,
          hdr, db_cipher, &hdr->chksum[0], (u_int8_t *)persist,
          hdr->len - hdrsize, is_hmac)) != 0)) {
            __db_errx(dbenv, "log record checksum mismatch");
            goto err;
      }

      /*
       * If the log is readable so far and we're doing system initialization,
       * set the region's persistent information based on the headers.
       *
       * Override the current log file size.
       */
      if (set_persist) {
            lp = dblp->reginfo.primary;
            lp->log_size = persist->log_size;
            lp->persist.version = persist->version;
      }
      if (versionp != NULL)
            *versionp = persist->version;

err:  if (fname != NULL)
            __os_free(dbenv, fname);
      if (ret == 0 && fhpp != NULL)
            *fhpp = fhp;
      else
            /* Must close on error or if we only used it locally. */
            (void)__os_closehandle(dbenv, fhp);
      if (tmp != NULL)
            __os_free(dbenv, tmp);

      if (statusp != NULL)
            *statusp = status;

      return (ret);
}

/*
 * __log_env_refresh --
 *    Clean up after the log system on a close or failed open.
 *
 * PUBLIC: int __log_env_refresh __P((DB_ENV *));
 */
int
__log_env_refresh(dbenv)
      DB_ENV *dbenv;
{
      DB_LOG *dblp;
      LOG *lp;
      REGINFO *reginfo;
      struct __fname *fnp;
      struct __db_filestart *filestart;
      int ret, t_ret;

      dblp = dbenv->lg_handle;
      reginfo = &dblp->reginfo;
      lp = reginfo->primary;
      ret = 0;

      /*
       * Flush the log if it's private -- there's no Berkeley DB guarantee
       * that this gets done, but in case the application has forgotten to
       * flush for durability, it's the polite thing to do.
       */
      if (F_ISSET(dbenv, DB_ENV_PRIVATE) &&
          (t_ret = __log_flush(dbenv, NULL)) != 0 && ret == 0)
            ret = t_ret;

      /* We may have opened files as part of XA; if so, close them. */
      if ((t_ret = __dbreg_close_files(dbenv, 0)) != 0 && ret == 0)
            ret = t_ret;

      /*
       * After we close the files, check for any unlogged closes left in
       * the shared memory queue.  If we find any, try to log it, otherwise
       * return the error.  We cannot say the environment was closed
       * cleanly.
       */
      MUTEX_LOCK(dbenv, lp->mtx_filelist);
      SH_TAILQ_FOREACH(fnp, &lp->fq, q, __fname)
            if (F_ISSET(fnp, DB_FNAME_NOTLOGGED) &&
                (t_ret = __dbreg_close_id_int(
                dbenv, fnp, DBREG_CLOSE, 1)) != 0)
                  ret = t_ret;
      MUTEX_UNLOCK(dbenv, lp->mtx_filelist);

      /*
       * If a private region, return the memory to the heap.  Not needed for
       * filesystem-backed or system shared memory regions, that memory isn't
       * owned by any particular process.
       */
      if (F_ISSET(dbenv, DB_ENV_PRIVATE)) {
            /* Discard the flush mutex. */
            if ((t_ret =
                __mutex_free(dbenv, &lp->mtx_flush)) != 0 && ret == 0)
                  ret = t_ret;

            /* Discard the buffer. */
            __env_alloc_free(reginfo, R_ADDR(reginfo, lp->buffer_off));

            /* Discard stack of free file IDs. */
            if (lp->free_fid_stack != INVALID_ROFF)
                  __env_alloc_free(reginfo,
                      R_ADDR(reginfo, lp->free_fid_stack));

            /* Discard the list of in-memory log file markers. */
            while ((filestart = SH_TAILQ_FIRST(&lp->logfiles,
                __db_filestart)) != NULL) {
                  SH_TAILQ_REMOVE(&lp->logfiles, filestart, links,
                      __db_filestart);
                  __env_alloc_free(reginfo, filestart);
            }

            while ((filestart = SH_TAILQ_FIRST(&lp->free_logfiles,
                __db_filestart)) != NULL) {
                  SH_TAILQ_REMOVE(&lp->free_logfiles, filestart, links,
                      __db_filestart);
                  __env_alloc_free(reginfo, filestart);
            }

            /* Discard replication bulk buffer. */
            if (lp->bulk_buf != INVALID_ROFF) {
                  __env_alloc_free(reginfo,
                      R_ADDR(reginfo, lp->bulk_buf));
                  lp->bulk_buf = INVALID_ROFF;
            }
      }

      /* Discard the per-thread DBREG mutex. */
      if ((t_ret = __mutex_free(dbenv, &dblp->mtx_dbreg)) != 0 && ret == 0)
            ret = t_ret;

      /* Detach from the region. */
      if ((t_ret = __env_region_detach(dbenv, reginfo, 0)) != 0 && ret == 0)
            ret = t_ret;

      /* Close open files, release allocated memory. */
      if (dblp->lfhp != NULL) {
            if ((t_ret =
                __os_closehandle(dbenv, dblp->lfhp)) != 0 && ret == 0)
                  ret = t_ret;
            dblp->lfhp = NULL;
      }
      if (dblp->dbentry != NULL)
            __os_free(dbenv, dblp->dbentry);

      __os_free(dbenv, dblp);

      dbenv->lg_handle = NULL;
      return (ret);
}

/*
 * __log_get_cached_ckp_lsn --
 *    Retrieve any last checkpoint LSN that we may have found on startup.
 *
 * PUBLIC: int __log_get_cached_ckp_lsn __P((DB_ENV *, DB_LSN *));
 */
int
__log_get_cached_ckp_lsn(dbenv, ckp_lsnp)
      DB_ENV *dbenv;
      DB_LSN *ckp_lsnp;
{
      DB_LOG *dblp;
      LOG *lp;

      dblp = dbenv->lg_handle;
      lp = (LOG *)dblp->reginfo.primary;

      LOG_SYSTEM_LOCK(dbenv);
      *ckp_lsnp = lp->cached_ckp_lsn;
      LOG_SYSTEM_UNLOCK(dbenv);

      return (0);
}

/*
 * __log_region_mutex_count --
 *    Return the number of mutexes the log region will need.
 *
 * PUBLIC: u_int32_t __log_region_mutex_count __P((DB_ENV *));
 */
u_int32_t
__log_region_mutex_count(dbenv)
      DB_ENV *dbenv;
{
      /*
       * We need a few assorted mutexes, and one per transaction waiting
       * on the group commit list.  We can't know how many that will be,
       * but it should be bounded by the maximum active transactions.
       */
      return (dbenv->tx_max + 5);
}

/*
 * __log_region_size --
 *    Return the amount of space needed for the log region.
 *    Make the region large enough to hold txn_max transaction
 *    detail structures  plus some space to hold thread handles
 *    and the beginning of the alloc region and anything we
 *    need for mutex system resource recording.
 */
static size_t
__log_region_size(dbenv)
      DB_ENV *dbenv;
{
      size_t s;

      s = dbenv->lg_regionmax + dbenv->lg_bsize;

      /*
       * If running with replication, add in space for bulk buffer.
       * Allocate a megabyte and a little bit more space.
       */
      if (IS_ENV_REPLICATED(dbenv))
            s += MEGABYTE;

      return (s);
}

/*
 * __log_vtruncate
 *    This is a virtual truncate.  We set up the log indicators to
 * make everyone believe that the given record is the last one in the
 * log.  Returns with the next valid LSN (i.e., the LSN of the next
 * record to be written). This is used in replication to discard records
 * in the log file that do not agree with the master.
 *
 * PUBLIC: int __log_vtruncate __P((DB_ENV *, DB_LSN *, DB_LSN *, DB_LSN *));
 */
int
__log_vtruncate(dbenv, lsn, ckplsn, trunclsn)
      DB_ENV *dbenv;
      DB_LSN *lsn, *ckplsn, *trunclsn;
{
      DBT log_dbt;
      DB_LOG *dblp;
      DB_LOGC *logc;
      LOG *lp;
      u_int32_t bytes, len;
      int ret, t_ret;

      /* Need to find out the length of this soon-to-be-last record. */
      if ((ret = __log_cursor(dbenv, &logc)) != 0)
            return (ret);
      memset(&log_dbt, 0, sizeof(log_dbt));
      ret = __logc_get(logc, lsn, &log_dbt, DB_SET);
      len = logc->len;
      if ((t_ret = __logc_close(logc)) != 0 && ret == 0)
            ret = t_ret;
      if (ret != 0)
            return (ret);

      /* Now do the truncate. */
      dblp = dbenv->lg_handle;
      lp = (LOG *)dblp->reginfo.primary;

      LOG_SYSTEM_LOCK(dbenv);

      /*
       * Flush the log so we can simply initialize the in-memory buffer
       * after the truncate.
       */
      if ((ret = __log_flush_int(dblp, NULL, 0)) != 0)
            goto err;

      lp->lsn = *lsn;
      lp->len = len;
      lp->lsn.offset += lp->len;

      if (lp->db_log_inmemory &&
          (ret = __log_inmem_lsnoff(dblp, &lp->lsn, &lp->b_off)) != 0)
            goto err;

      /*
       * I am going to assume that the number of bytes written since
       * the last checkpoint doesn't exceed a 32-bit number.
       */
      DB_ASSERT(dbenv, lp->lsn.file >= ckplsn->file);
      bytes = 0;
      if (ckplsn->file != lp->lsn.file) {
            bytes = lp->log_size - ckplsn->offset;
            if (lp->lsn.file > ckplsn->file + 1)
                  bytes += lp->log_size *
                      ((lp->lsn.file - ckplsn->file) - 1);
            bytes += lp->lsn.offset;
      } else
            bytes = lp->lsn.offset - ckplsn->offset;

      lp->stat.st_wc_mbytes += bytes / MEGABYTE;
      lp->stat.st_wc_bytes += bytes % MEGABYTE;

      /*
       * If the synced lsn is greater than our new end of log, reset it
       * to our current end of log.
       */
      MUTEX_LOCK(dbenv, lp->mtx_flush);
      if (LOG_COMPARE(&lp->s_lsn, lsn) > 0)
            lp->s_lsn = lp->lsn;
      MUTEX_UNLOCK(dbenv, lp->mtx_flush);

      /* Initialize the in-region buffer to a pristine state. */
      ZERO_LSN(lp->f_lsn);
      lp->w_off = lp->lsn.offset;

      if (trunclsn != NULL)
            *trunclsn = lp->lsn;

      /* Truncate the log to the new point. */
      if ((ret = __log_zero(dbenv, &lp->lsn)) != 0)
            goto err;

err:  LOG_SYSTEM_UNLOCK(dbenv);
      return (ret);
}

/*
 * __log_is_outdated --
 *    Used by the replication system to identify if a client's logs are too
 *    old.
 *
 * PUBLIC: int __log_is_outdated __P((DB_ENV *, u_int32_t, int *));
 */
int
__log_is_outdated(dbenv, fnum, outdatedp)
      DB_ENV *dbenv;
      u_int32_t fnum;
      int *outdatedp;
{
      DB_LOG *dblp;
      LOG *lp;
      char *name;
      int ret;
      u_int32_t cfile;
      struct __db_filestart *filestart;

      dblp = dbenv->lg_handle;

      /*
       * The log represented by dbenv is compared to the file number passed
       * in fnum.  If the log file fnum does not exist and is lower-numbered
       * than the current logs, return *outdatedp non-zero, else we return 0.
       */
      if (F_ISSET(dbenv, DB_ENV_LOG_INMEMORY)) {
            LOG_SYSTEM_LOCK(dbenv);
            lp = (LOG *)dblp->reginfo.primary;
            filestart = SH_TAILQ_FIRST(&lp->logfiles, __db_filestart);
            *outdatedp = filestart == NULL ? 0 : (fnum < filestart->file);
            LOG_SYSTEM_UNLOCK(dbenv);
            return (0);
      }

      *outdatedp = 0;
      if ((ret = __log_name(dblp, fnum, &name, NULL, 0)) != 0)
            return (ret);

      /* If the file exists, we're just fine. */
      if (__os_exists(dbenv, name, NULL) == 0)
            goto out;

      /*
       * It didn't exist, decide if the file number is too big or
       * too little.  If it's too little, then we need to indicate
       * that the LSN is outdated.
       */
      LOG_SYSTEM_LOCK(dbenv);
      lp = (LOG *)dblp->reginfo.primary;
      cfile = lp->lsn.file;
      LOG_SYSTEM_UNLOCK(dbenv);

      if (cfile > fnum)
            *outdatedp = 1;
out:  __os_free(dbenv, name);
      return (ret);
}

/*
 * __log_zero --
 *    Zero out the tail of a log after a truncate.
 *
 * PUBLIC: int __log_zero __P((DB_ENV *, DB_LSN *));
 */
int
__log_zero(dbenv, from_lsn)
      DB_ENV *dbenv;
      DB_LSN *from_lsn;
{
      DB_FH *fhp;
      DB_LOG *dblp;
      LOG *lp;
      struct __db_filestart *filestart, *nextstart;
      size_t nbytes, len, nw;
      u_int32_t fn, mbytes, bytes;
      u_int8_t buf[4096];
      int ret;
      char *fname;

      dblp = dbenv->lg_handle;
      lp = (LOG *)dblp->reginfo.primary;
      DB_ASSERT(dbenv, LOG_COMPARE(from_lsn, &lp->lsn) <= 0);
      if (LOG_COMPARE(from_lsn, &lp->lsn) > 0) {
            __db_errx(dbenv,
                "Warning: truncating to point beyond end of log");
            return (0);
      }

      if (lp->db_log_inmemory) {
            /*
             * Remove the files that are invalidated by this truncate.
             */
            for (filestart = SH_TAILQ_FIRST(&lp->logfiles, __db_filestart);
                filestart != NULL; filestart = nextstart) {
                  nextstart = SH_TAILQ_NEXT(filestart,
                      links, __db_filestart);
                  if (filestart->file > from_lsn->file) {
                        SH_TAILQ_REMOVE(&lp->logfiles,
                            filestart, links, __db_filestart);
                        SH_TAILQ_INSERT_HEAD(&lp->free_logfiles,
                            filestart, links, __db_filestart);
                  }
            }

            return (0);
      }

      /* Close any open file handles so unlinks don't fail. */
      if (dblp->lfhp != NULL) {
            (void)__os_closehandle(dbenv, dblp->lfhp);
            dblp->lfhp = NULL;
      }

      /* Throw away any extra log files that we have around. */
      for (fn = from_lsn->file + 1;; fn++) {
            if (__log_name(dblp, fn, &fname, &fhp, DB_OSO_RDONLY) != 0) {
                  __os_free(dbenv, fname);
                  break;
            }
            (void)__os_closehandle(dbenv, fhp);
            (void)time(&lp->timestamp);
            ret = __os_unlink(dbenv, fname);
            __os_free(dbenv, fname);
            if (ret != 0)
                  return (ret);
      }

      /* We removed some log files; have to 0 to end of file. */
      if ((ret =
          __log_name(dblp, from_lsn->file, &fname, &dblp->lfhp, 0)) != 0)
            return (ret);
      __os_free(dbenv, fname);
      if ((ret = __os_ioinfo(dbenv,
          NULL, dblp->lfhp, &mbytes, &bytes, NULL)) != 0)
            goto err;
      DB_ASSERT(dbenv, (mbytes * MEGABYTE + bytes) >= from_lsn->offset);
      len = (mbytes * MEGABYTE + bytes) - from_lsn->offset;

      memset(buf, 0, sizeof(buf));

      /* Initialize the write position. */
      if ((ret = __os_seek(dbenv, dblp->lfhp, 0, 0, from_lsn->offset)) != 0)
            goto err;

      while (len > 0) {
            nbytes = len > sizeof(buf) ? sizeof(buf) : len;
            if ((ret =
                __os_write(dbenv, dblp->lfhp, buf, nbytes, &nw)) != 0)
                  goto err;
            len -= nbytes;
      }

err:  (void)__os_closehandle(dbenv, dblp->lfhp);
      dblp->lfhp = NULL;

      return (ret);
}

/*
 * __log_inmem_lsnoff --
 *    Find the offset in the buffer of a given LSN.
 *
 * PUBLIC: int __log_inmem_lsnoff __P((DB_LOG *, DB_LSN *, size_t *));
 */
int
__log_inmem_lsnoff(dblp, lsnp, offsetp)
      DB_LOG *dblp;
      DB_LSN *lsnp;
      size_t *offsetp;
{
      LOG *lp;
      struct __db_filestart *filestart;

      lp = (LOG *)dblp->reginfo.primary;

      SH_TAILQ_FOREACH(filestart, &lp->logfiles, links, __db_filestart)
            if (filestart->file == lsnp->file) {
                  *offsetp =
                      (filestart->b_off + lsnp->offset) % lp->buffer_size;
                  return (0);
            }

      return (DB_NOTFOUND);
}

/*
 * __log_inmem_newfile --
 *    Records the offset of the beginning of a new file in the in-memory
 *    buffer.
 *
 * PUBLIC: int __log_inmem_newfile __P((DB_LOG *, u_int32_t));
 */
int
__log_inmem_newfile(dblp, file)
      DB_LOG *dblp;
      u_int32_t file;
{
      HDR hdr;
      LOG *lp;
      struct __db_filestart *filestart;
      int ret;
#ifdef DIAGNOSTIC
      struct __db_filestart *first, *last;
#endif

      lp = (LOG *)dblp->reginfo.primary;

      /*
       * If the log buffer is empty, reuse the filestart entry.
       */
      filestart = SH_TAILQ_FIRST(&lp->logfiles, __db_filestart);
      if (filestart != NULL &&
          RINGBUF_LEN(lp, filestart->b_off, lp->b_off) <=
          sizeof(HDR) + sizeof(LOGP)) {
            filestart->file = file;
            filestart->b_off = lp->b_off;
            return (0);
      }

      /*
       * We write an empty header at the end of every in-memory log file.
       * This is used during cursor traversal to indicate when to switch the
       * LSN to the next file.
       */
      if (file > 1) {
            memset(&hdr, 0, sizeof(HDR));
            __log_inmem_copyin(dblp, lp->b_off, &hdr, sizeof(HDR));
            lp->b_off = (lp->b_off + sizeof(HDR)) % lp->buffer_size;
      }

      filestart = SH_TAILQ_FIRST(&lp->free_logfiles, __db_filestart);
      if (filestart == NULL) {
            if ((ret = __env_alloc(&dblp->reginfo,
                sizeof(struct __db_filestart), &filestart)) != 0)
                  return (ret);
            memset(filestart, 0, sizeof(*filestart));
      } else
            SH_TAILQ_REMOVE(&lp->free_logfiles, filestart,
                links, __db_filestart);

      filestart->file = file;
      filestart->b_off = lp->b_off;

#ifdef DIAGNOSTIC
      first = SH_TAILQ_FIRST(&lp->logfiles, __db_filestart);
      last = SH_TAILQ_LAST(&(lp)->logfiles, links, __db_filestart);

      /* Check that we don't wrap. */
      DB_ASSERT(dblp->dbenv, !first || first == last ||
          RINGBUF_LEN(lp, first->b_off, lp->b_off) ==
          RINGBUF_LEN(lp, first->b_off, last->b_off) +
          RINGBUF_LEN(lp, last->b_off, lp->b_off));
#endif

      SH_TAILQ_INSERT_TAIL(&lp->logfiles, filestart, links);
      return (0);
}

/*
 * __log_inmem_chkspace --
 *    Ensure that the requested amount of space is available in the buffer,
 *    and invalidate the region.
 *      Note: assumes that the region lock is held on entry.
 *
 * PUBLIC: int __log_inmem_chkspace __P((DB_LOG *, size_t));
 */
int
__log_inmem_chkspace(dblp, len)
      DB_LOG *dblp;
      size_t len;
{
      DB_ENV *dbenv;
      LOG *lp;
      DB_LSN active_lsn, old_active_lsn;
      struct __db_filestart *filestart;
      int ret;

      dbenv = dblp->dbenv;
      lp = dblp->reginfo.primary;

      DB_ASSERT(dbenv, lp->db_log_inmemory);

      /*
       * Allow room for an extra header so that we don't need to check for
       * space when switching files.
       */
      len += sizeof(HDR);

      /*
       * If transactions are enabled and we're about to fill available space,
       * update the active LSN and recheck.  If transactions aren't enabled,
       * don't even bother checking: in that case we can always overwrite old
       * log records, because we're never going to abort.
       */
      while (TXN_ON(dbenv) &&
          RINGBUF_LEN(lp, lp->b_off, lp->a_off) <= len) {
            old_active_lsn = lp->active_lsn;
            active_lsn = lp->lsn;

            /*
             * Drop the log region lock so we don't hold it while
             * taking the transaction region lock.
             */
            LOG_SYSTEM_UNLOCK(dbenv);
            if ((ret = __txn_getactive(dbenv, &active_lsn)) != 0)
                  return (ret);
            LOG_SYSTEM_LOCK(dbenv);
            active_lsn.offset = 0;

            /* If we didn't make any progress, give up. */
            if (LOG_COMPARE(&active_lsn, &old_active_lsn) == 0) {
                  __db_errx(dbenv,
      "In-memory log buffer is full (an active transaction spans the buffer)");
                  return (DB_LOG_BUFFER_FULL);
            }

            /* Make sure we're moving the region LSN forwards. */
            if (LOG_COMPARE(&active_lsn, &lp->active_lsn) > 0) {
                  lp->active_lsn = active_lsn;
                  (void)__log_inmem_lsnoff(dblp, &active_lsn,
                      &lp->a_off);
            }
      }

      /*
       * Remove the first file if it is invalidated by this write.
       * Log records can't be bigger than a file, so we only need to
       * check the first file.
       */
      filestart = SH_TAILQ_FIRST(&lp->logfiles, __db_filestart);
      if (filestart != NULL &&
          RINGBUF_LEN(lp, lp->b_off, filestart->b_off) <= len) {
            SH_TAILQ_REMOVE(&lp->logfiles, filestart,
                links, __db_filestart);
            SH_TAILQ_INSERT_HEAD(&lp->free_logfiles, filestart,
                links, __db_filestart);
            lp->f_lsn.file = filestart->file + 1;
      }

      return (0);
}

/*
 * __log_inmem_copyout --
 *    Copies the given number of bytes from the buffer -- no checking.
 *      Note: assumes that the region lock is held on entry.
 *
 * PUBLIC: void __log_inmem_copyout __P((DB_LOG *, size_t, void *, size_t));
 */
void
__log_inmem_copyout(dblp, offset, buf, size)
      DB_LOG *dblp;
      size_t offset;
      void *buf;
      size_t size;
{
      LOG *lp;
      size_t nbytes;

      lp = (LOG *)dblp->reginfo.primary;
      nbytes = (offset + size < lp->buffer_size) ?
          size : lp->buffer_size - offset;
      memcpy(buf, dblp->bufp + offset, nbytes);
      if (nbytes < size)
            memcpy((u_int8_t *)buf + nbytes, dblp->bufp, size - nbytes);
}

/*
 * __log_inmem_copyin --
 *    Copies the given number of bytes into the buffer -- no checking.
 *      Note: assumes that the region lock is held on entry.
 *
 * PUBLIC: void __log_inmem_copyin __P((DB_LOG *, size_t, void *, size_t));
 */
void
__log_inmem_copyin(dblp, offset, buf, size)
      DB_LOG *dblp;
      size_t offset;
      void *buf;
      size_t size;
{
      LOG *lp;
      size_t nbytes;

      lp = (LOG *)dblp->reginfo.primary;
      nbytes = (offset + size < lp->buffer_size) ?
          size : lp->buffer_size - offset;
      memcpy(dblp->bufp + offset, buf, nbytes);
      if (nbytes < size)
            memcpy(dblp->bufp, (u_int8_t *)buf + nbytes, size - nbytes);
}

/*
 * __log_set_version --
 *    Sets the current version of the log subsystem to the given version.
 *    Essentially this modifies the lp->persist.version field in the
 *    shared memory region.  Called when region is initially created
 *    and when replication is starting up or finds a new master.
 *
 * PUBLIC: void __log_set_version __P((DB_ENV *, u_int32_t));
 */
void
__log_set_version(dbenv, newver)
      DB_ENV *dbenv;
      u_int32_t newver;
{
      DB_LOG *dblp;
      LOG *lp;

      dblp = dbenv->lg_handle;
      lp = (LOG *)dblp->reginfo.primary;
      /*
       * We should be able to update this atomically without locking.
       */
      lp->persist.version = newver;
}

/*
 * __log_get_oldversion --
 *    Returns the last version of log that this environment was working
 *    with.  Since there could be several versions of log files, if
 *    the user upgraded and didn't log archive, we check the version
 *    of the first log file, compare it to the last log file.  If those
 *    are different, then there is an older log existing, and we then
 *    walk backward in the log files looking for the version of the
 *    most recent older log file.
 *
 * PUBLIC: int __log_get_oldversion __P((DB_ENV *, u_int32_t *));
 */
int
__log_get_oldversion(dbenv, ver)
      DB_ENV *dbenv;
      u_int32_t *ver;
{
      DBT rec;
      DB_LOG *dblp;
      DB_LOGC *logc;
      DB_LSN lsn;
      LOG *lp;
      u_int32_t firstfnum, fnum, lastver, oldver;
      int ret, t_ret;

      dblp = dbenv->lg_handle;
      lp = dblp->reginfo.primary;

      logc = NULL;
      ret = 0;
      oldver = DB_LOGVERSION;
      /*
       * If we're in-memory logs we're always the current version.
       */
      if (lp->db_log_inmemory) {
            *ver = oldver;
            return (0);
      }
      memset(&rec, 0, sizeof(rec));
      if ((ret = __log_cursor(dbenv, &logc)) != 0)
            goto err;
      /*
       * Get the version numbers of the first and last log files.
       */
      if ((ret = __logc_get(logc, &lsn, &rec, DB_FIRST)) != 0) {
            /*
             * If there is no log file, we'll get DB_NOTFOUND.
             * If we get that, set the version to the current.
             */
            if (ret == DB_NOTFOUND)
                  ret = 0;
            goto err;
      }
      firstfnum = lsn.file;
      if ((ret = __logc_get(logc, &lsn, &rec, DB_LAST)) != 0)
            goto err;
      if ((ret = __log_valid(dblp, firstfnum, 0, NULL, 0,
          NULL, &oldver)) != 0)
            goto err;
      /*
       * If the first and last LSN are in the same file, then we
       * already have the version in oldver.  Return it.
       */
      if (firstfnum == lsn.file)
            goto err;

      /*
       * Otherwise they're in different files and we call __log_valid
       * to get the version numbers in both files.
       */
      if ((ret = __log_valid(dblp, lsn.file, 0, NULL, 0,
          NULL, &lastver)) != 0)
            goto err;
      /*
       * If the version numbers are different, walk backward getting
       * the version of each log file until we find one that is
       * different than the last.
       */
      if (oldver != lastver) {
            for (fnum = lsn.file - 1; fnum >= firstfnum; fnum--) {
                  if ((ret = __log_valid(dblp, fnum, 0, NULL, 0,
                      NULL, &oldver)) != 0)
                        goto err;
                  if (oldver != lastver)
                        break;
            }
      }
err:  if (logc != NULL && ((t_ret = __logc_close(logc)) != 0) && ret == 0)
            ret = t_ret;
      if (ret == 0 && ver != NULL)
            *ver = oldver;
      return (ret);
}

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