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mp_fopen.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996-2005
 *    Sleepycat Software.  All rights reserved.
 *
 * $Id: mp_fopen.c,v 12.16 2005/10/31 02:22:31 bostic Exp $
 */

#include "db_config.h"

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

#include <string.h>
#endif

#include "db_int.h"
#include "dbinc/db_shash.h"
#include "dbinc/log.h"
#include "dbinc/mp.h"

/*
 * __memp_fopen_pp --
 *    DB_MPOOLFILE->open pre/post processing.
 *
 * PUBLIC: int __memp_fopen_pp
 * PUBLIC:     __P((DB_MPOOLFILE *, const char *, u_int32_t, int, size_t));
 */
int
__memp_fopen_pp(dbmfp, path, flags, mode, pagesize)
      DB_MPOOLFILE *dbmfp;
      const char *path;
      u_int32_t flags;
      int mode;
      size_t pagesize;
{
      DB_ENV *dbenv;
      DB_THREAD_INFO *ip;
      int ret;

      dbenv = dbmfp->dbenv;

      PANIC_CHECK(dbenv);

      /* Validate arguments. */
      if ((ret = __db_fchk(dbenv, "DB_MPOOLFILE->open", flags,
          DB_CREATE | DB_DIRECT | DB_EXTENT |
          DB_NOMMAP | DB_ODDFILESIZE | DB_RDONLY | DB_TRUNCATE)) != 0)
            return (ret);

      /*
       * Require a non-zero, power-of-two pagesize, smaller than the
       * clear length.
       */
      if (pagesize == 0 || !POWER_OF_TWO(pagesize)) {
            __db_err(dbenv,
                "DB_MPOOLFILE->open: page sizes must be a power-of-2");
            return (EINVAL);
      }
      if (dbmfp->clear_len > pagesize) {
            __db_err(dbenv,
                "DB_MPOOLFILE->open: clear length larger than page size");
            return (EINVAL);
      }

      /* Read-only checks, and local flag. */
      if (LF_ISSET(DB_RDONLY) && path == NULL) {
            __db_err(dbenv,
                "DB_MPOOLFILE->open: temporary files can't be readonly");
            return (EINVAL);
      }

      ENV_ENTER(dbenv, ip);
      REPLICATION_WRAP(dbenv,
          (__memp_fopen(dbmfp, NULL, path, flags, mode, pagesize)), ret);
      ENV_LEAVE(dbenv, ip);
      return (ret);
}

/*
 * __memp_fopen --
 *    DB_MPOOLFILE->open.
 *
 * PUBLIC: int __memp_fopen __P((DB_MPOOLFILE *,
 * PUBLIC:     MPOOLFILE *, const char *, u_int32_t, int, size_t));
 */
int
__memp_fopen(dbmfp, mfp, path, flags, mode, pgsize)
      DB_MPOOLFILE *dbmfp;
      MPOOLFILE *mfp;
      const char *path;
      u_int32_t flags;
      int mode;
      size_t pgsize;
{
      DB_ENV *dbenv;
      DB_MPOOL *dbmp;
      DB_MPOOLFILE *tmp_dbmfp;
      MPOOL *mp;
      db_pgno_t last_pgno;
      size_t maxmap;
      u_int32_t mbytes, bytes, oflags, pagesize;
      int created_fileid, refinc, ret;
      char *rpath;
      void *p;

      dbenv = dbmfp->dbenv;
      dbmp = dbenv->mp_handle;
      mp = dbmp->reginfo[0].primary;
      created_fileid = refinc = ret = 0;
      rpath = NULL;

      /*
       * We're keeping the page size as a size_t in the public API, but
       * it's a u_int32_t everywhere internally.
       */
      pagesize = (u_int32_t)pgsize;

      /*
       * We're called internally with a specified mfp, in which case the
       * path is NULL, but we'll get the path from the underlying region
       * information.  Otherwise, if the path is NULL, it's a temporary
       * file -- we know we can't join any existing files, and we'll delay
       * the open until we actually need to write the file.
       */
      DB_ASSERT(mfp == NULL || path == NULL);

      /* If this handle is already open, return. */
      if (F_ISSET(dbmfp, MP_OPEN_CALLED))
            return (0);

      if (path == NULL && mfp == NULL)
            goto alloc;

      /*
       * If there's no backing file, we can join existing files in the cache,
       * but there's nothing to read from disk.
       */
      if (FLD_ISSET(dbmfp->config_flags, DB_MPOOL_NOFILE))
            goto check_mpoolfile;

      /*
       * Our caller may be able to tell us which underlying MPOOLFILE we
       * need a handle for.
       */
      if (mfp != NULL) {
            /*
             * Deadfile can only be set if mpf_cnt goes to zero (or if we
             * failed creating the file DB_AM_DISCARD).  Increment the ref
             * count so the file cannot become dead and be unlinked.
             */
            MUTEX_LOCK(dbenv, mfp->mutex);
            if (!mfp->deadfile) {
                  ++mfp->mpf_cnt;
                  refinc = 1;
            }
            MUTEX_UNLOCK(dbenv, mfp->mutex);

            /*
             * Test one last time to see if the file is dead -- it may have
             * been removed.  This happens when a checkpoint trying to open
             * the file to flush a buffer races with the Db::remove method.
             * The error will be ignored, so don't output an error message.
             */
            if (mfp->deadfile)
                  return (EINVAL);
      }

      /* Convert MP open flags to DB OS-layer open flags. */
      oflags = 0;
      if (LF_ISSET(DB_CREATE))
            oflags |= DB_OSO_CREATE;
      if (LF_ISSET(DB_DIRECT))
            oflags |= DB_OSO_DIRECT;
      if (LF_ISSET(DB_RDONLY)) {
            F_SET(dbmfp, MP_READONLY);
            oflags |= DB_OSO_RDONLY;
      }

      /*
       * XXX
       * A grievous layering violation, the DB_DSYNC_DB flag was left in
       * the DB_ENV structure and not driven through the cache API.  This
       * needs to be fixed when the general API configuration is fixed.
       */
      if (F_ISSET(dbenv, DB_ENV_DSYNC_DB))
            oflags |= DB_OSO_DSYNC;

      /*
       * Get the real name for this file and open it.
       *
       * Supply a page size so os_open can decide whether to turn buffering
       * off if the DB_DIRECT_DB flag is set.
       *
       * Acquire the region lock if we're using a path from an underlying
       * MPOOLFILE -- there's a race in accessing the path name stored in
       * the region, __memp_nameop may be simultaneously renaming the file.
       */
      if (mfp != NULL) {
            MPOOL_SYSTEM_LOCK(dbenv);
            path = R_ADDR(dbmp->reginfo, mfp->path_off);
      }
      if ((ret =
          __db_appname(dbenv, DB_APP_DATA, path, 0, NULL, &rpath)) == 0)
            ret = __os_open_extend(dbenv,
                rpath, (u_int32_t)pagesize, oflags, mode, &dbmfp->fhp);
      if (mfp != NULL)
            MPOOL_SYSTEM_UNLOCK(dbenv);

      if (ret != 0) {
            /* If it's a Queue extent file, it may not exist, that's OK. */
            if (!LF_ISSET(DB_EXTENT))
                  __db_err(dbenv, "%s: %s", rpath, db_strerror(ret));
            goto err;
      }

      /*
       * Cache file handles are shared, and have mutexes to protect the
       * underlying file handle across seek and read/write calls.
       */
      dbmfp->fhp->ref = 1;
      if ((ret = __mutex_alloc(
          dbenv, MTX_MPOOL_FH, DB_MUTEX_THREAD, &dbmfp->fhp->mtx_fh)) != 0)
            goto err;

      /*
       * Figure out the file's size.
       *
       * !!!
       * We can't use off_t's here, or in any code in the mainline library
       * for that matter.  (We have to use them in the os stubs, of course,
       * as there are system calls that take them as arguments.)  The reason
       * is some customers build in environments where an off_t is 32-bits,
       * but still run where offsets are 64-bits, and they pay us a lot of
       * money.
       */
      if ((ret = __os_ioinfo(
          dbenv, rpath, dbmfp->fhp, &mbytes, &bytes, NULL)) != 0) {
            __db_err(dbenv, "%s: %s", rpath, db_strerror(ret));
            goto err;
      }

      /*
       * Get the file id if we weren't given one.  Generated file id's
       * don't use timestamps, otherwise there'd be no chance of any
       * other process joining the party.
       */
      if (!F_ISSET(dbmfp, MP_FILEID_SET)) {
            if  ((ret = __os_fileid(dbenv, rpath, 0, dbmfp->fileid)) != 0)
                  goto err;
            created_fileid = 1;
      }

      if (mfp != NULL)
            goto have_mfp;

check_mpoolfile:
      /*
       * Walk the list of MPOOLFILE's, looking for a matching file.
       *
       * The fileID is a filesystem unique number (e.g., a UNIX dev/inode
       * pair) plus a timestamp.  If files are removed and created in less
       * than a second, the fileID can be repeated.  The problem with
       * repetition happens when the file that previously had the fileID
       * value still has pages in the pool, since we don't want to use them
       * to satisfy requests for the new file.
       *
       * Because the DB_TRUNCATE flag reuses the dev/inode pair, repeated
       * opens with that flag set guarantees matching fileIDs when the
       * machine can open a file and then re-open with truncate within a
       * second.  For this reason, we pass that flag down, and, if we find
       * a matching entry, we ensure that it's never found again, and we
       * create a new entry for the current request.
       */
      MPOOL_SYSTEM_LOCK(dbenv);
      for (mfp = SH_TAILQ_FIRST(&mp->mpfq, __mpoolfile);
          mfp != NULL; mfp = SH_TAILQ_NEXT(mfp, q, __mpoolfile)) {
            /* Skip dead files and temporary files. */
            if (mfp->deadfile || F_ISSET(mfp, MP_TEMP))
                  continue;

            /*
             * Any remaining DB_MPOOL_NOFILE databases are in-memory
             * named databases and need only match other in-memory
             * databases with the same name.
             */
            if (FLD_ISSET(dbmfp->config_flags, DB_MPOOL_NOFILE)) {
                  if (!mfp->no_backing_file)
                        continue;

                  if (strcmp(path, R_ADDR(dbmp->reginfo, mfp->path_off)))
                        continue;

                  /*
                   * We matched an in-memory file; grab the fileid if
                   * it is set in the region, but not in the dbmfp.
                   */
                  if (!F_ISSET(dbmfp, MP_FILEID_SET))
                        __memp_set_fileid(dbmfp,
                            R_ADDR(dbmp->reginfo, mfp->fileid_off));
            } else
                  if (memcmp(dbmfp->fileid, R_ADDR(dbmp->reginfo,
                      mfp->fileid_off), DB_FILE_ID_LEN) != 0)
                        continue;

            /*
             * If the file is being truncated, remove it from the system
             * and create a new entry.
             *
             * !!!
             * We should be able to set mfp to NULL and break out of the
             * loop, but I like the idea of checking all the entries.
             */
            if (LF_ISSET(DB_TRUNCATE)) {
                  MUTEX_LOCK(dbenv, mfp->mutex);
                  mfp->deadfile = 1;
                  MUTEX_UNLOCK(dbenv, mfp->mutex);
                  continue;
            }

            /*
             * Some things about a file cannot be changed: the clear length,
             * page size, or LSN location.  However, if this is an attempt
             * to open a named in-memory file, we may not yet have that
             * information. so accept uninitialized entries.
             *
             * The file type can change if the application's pre- and post-
             * processing needs change.  For example, an application that
             * created a hash subdatabase in a database that was previously
             * all btree.
             *
             * !!!
             * We do not check to see if the pgcookie information changed,
             * or update it if it is.
             */
            if ((dbmfp->clear_len != DB_CLEARLEN_NOTSET &&
                mfp->clear_len != DB_CLEARLEN_NOTSET &&
                dbmfp->clear_len != mfp->clear_len) ||
                (pagesize != 0 && pagesize != mfp->stat.st_pagesize) ||
                (dbmfp->lsn_offset != -1 &&
                mfp->lsn_off != DB_LSN_OFF_NOTSET &&
                dbmfp->lsn_offset != mfp->lsn_off)) {
                  __db_err(dbenv,
                "%s: clear length, page size or LSN location changed",
                      path);
                  MPOOL_SYSTEM_UNLOCK(dbenv);
                  ret = EINVAL;
                  goto err;
            }

            /*
             * Check to see if this file has died while we waited.
             *
             * We normally don't lock the deadfile field when we read it as
             * we only care if the field is zero or non-zero.  We do lock
             * on read when searching for a matching MPOOLFILE so that two
             * threads of control don't race between setting the deadfile
             * bit and incrementing the reference count, that is, a thread
             * of control decrementing the reference count and then setting
             * deadfile because the reference count is 0 blocks us finding
             * the file without knowing it's about to be marked dead.
             */
            MUTEX_LOCK(dbenv, mfp->mutex);
            if (mfp->deadfile) {
                  MUTEX_UNLOCK(dbenv, mfp->mutex);
                  continue;
            }
            ++mfp->mpf_cnt;
            refinc = 1;
            MUTEX_UNLOCK(dbenv, mfp->mutex);

            /* Initialize any fields that are not yet set. */
            if (dbmfp->ftype != 0)
                  mfp->ftype = dbmfp->ftype;
            if (dbmfp->clear_len != DB_CLEARLEN_NOTSET)
                  mfp->clear_len = dbmfp->clear_len;
            if (dbmfp->lsn_offset != -1)
                  mfp->lsn_off = dbmfp->lsn_offset;

            break;
      }
      MPOOL_SYSTEM_UNLOCK(dbenv);

      if (mfp != NULL)
            goto have_mfp;

alloc:      /*
       * If we get here and we created a FILEID, then it's OK to set
       * the dbmfp as having its FILEID_SET, because we aren't trying
       * to match an existing file in the mpool.
       */
      if (created_fileid)
            F_SET(dbmfp, MP_FILEID_SET);
      /*
       * If we didn't find the file and this is an in-memory file, then
       *  the create flag should be set.
       */
      if (FLD_ISSET(dbmfp->config_flags, DB_MPOOL_NOFILE) &&
          !LF_ISSET(DB_CREATE)) {
            ret = ENOENT;
            goto err;
      }

      /* Allocate and initialize a new MPOOLFILE. */
      if ((ret = __memp_alloc(
          dbmp, dbmp->reginfo, NULL, sizeof(MPOOLFILE), NULL, &mfp)) != 0)
            goto err;
      memset(mfp, 0, sizeof(MPOOLFILE));
      mfp->mpf_cnt = 1;
      mfp->ftype = dbmfp->ftype;
      mfp->stat.st_pagesize = pagesize;
      mfp->lsn_off = dbmfp->lsn_offset;
      mfp->clear_len = dbmfp->clear_len;
      mfp->priority = dbmfp->priority;
      if (dbmfp->gbytes != 0 || dbmfp->bytes != 0) {
            mfp->maxpgno = (db_pgno_t)
                (dbmfp->gbytes * (GIGABYTE / mfp->stat.st_pagesize));
            mfp->maxpgno += (db_pgno_t)
                ((dbmfp->bytes + mfp->stat.st_pagesize - 1) /
                mfp->stat.st_pagesize);
      }
      if (FLD_ISSET(dbmfp->config_flags, DB_MPOOL_NOFILE))
            mfp->no_backing_file = 1;
      if (FLD_ISSET(dbmfp->config_flags, DB_MPOOL_UNLINK))
            mfp->unlink_on_close = 1;

      if (LF_ISSET(DB_DURABLE_UNKNOWN | DB_RDONLY))
            F_SET(mfp, MP_DURABLE_UNKNOWN);
      if (LF_ISSET(DB_DIRECT))
            F_SET(mfp, MP_DIRECT);
      if (LF_ISSET(DB_EXTENT))
            F_SET(mfp, MP_EXTENT);
      if (LF_ISSET(DB_TXN_NOT_DURABLE))
            F_SET(mfp, MP_NOT_DURABLE);
      F_SET(mfp, MP_CAN_MMAP);

      /*
       * An in-memory database with no name is a temp file.  Named
       * in-memory databases get an artificially  bumped reference
       * count so they don't disappear on close; they need a remove
       * to make them disappear.
       */
      if (path == NULL)
            F_SET(mfp, MP_TEMP);
      else if (FLD_ISSET(dbmfp->config_flags, DB_MPOOL_NOFILE))
            mfp->mpf_cnt++;

      if (path != NULL && !FLD_ISSET(dbmfp->config_flags, DB_MPOOL_NOFILE)) {
            /*
             * Don't permit files that aren't a multiple of the pagesize,
             * and find the number of the last page in the file, all the
             * time being careful not to overflow 32 bits.
             *
             * During verify or recovery, we might have to cope with a
             * truncated file; if the file size is not a multiple of the
             * page size, round down to a page, we'll take care of the
             * partial page outside the mpool system.
             */
            if (bytes % pagesize != 0) {
                  if (LF_ISSET(DB_ODDFILESIZE))
                        bytes -= (u_int32_t)(bytes % pagesize);
                  else {
                        __db_err(dbenv,
                "%s: file size not a multiple of the pagesize", rpath);
                        ret = EINVAL;
                        goto err;
                  }
            }

            /*
             * If the user specifies DB_MPOOL_LAST or DB_MPOOL_NEW on a
             * page get, we have to increment the last page in the file.
             * Figure it out and save it away.
             *
             * Note correction: page numbers are zero-based, not 1-based.
             */
            last_pgno = (db_pgno_t)(mbytes * (MEGABYTE / pagesize));
            last_pgno += (db_pgno_t)(bytes / pagesize);
            if (last_pgno != 0)
                  --last_pgno;
            mfp->orig_last_pgno = mfp->last_pgno = last_pgno;

            /*
             * Get the file ID if we weren't given one.  Generated file ID's
             * don't use timestamps, otherwise there'd be no chance of any
             * other process joining the party.
             */
            if (!F_ISSET(dbmfp, MP_FILEID_SET) &&
                (ret = __os_fileid(dbenv, rpath, 0, dbmfp->fileid)) != 0)
                  goto err;

      }

      /* Copy the file identification string into shared memory. */
      if (F_ISSET(dbmfp, MP_FILEID_SET)) {
            if ((ret = __memp_alloc(dbmp, dbmp->reginfo,
                NULL, DB_FILE_ID_LEN, &mfp->fileid_off, &p)) != 0)
                  goto err;
            memcpy(p, dbmfp->fileid, DB_FILE_ID_LEN);
      }

      /* Copy the file path into shared memory. */
      if (path != NULL) {
            if ((ret = __memp_alloc(dbmp, dbmp->reginfo,
                NULL, strlen(path) + 1, &mfp->path_off, &p)) != 0)
                  goto err;
            memcpy(p, path, strlen(path) + 1);
      }

      /* Copy the page cookie into shared memory. */
      if (dbmfp->pgcookie == NULL || dbmfp->pgcookie->size == 0) {
            mfp->pgcookie_len = 0;
            mfp->pgcookie_off = 0;
      } else {
            if ((ret = __memp_alloc(dbmp, dbmp->reginfo,
                NULL, dbmfp->pgcookie->size, &mfp->pgcookie_off, &p)) != 0)
                  goto err;
            memcpy(p, dbmfp->pgcookie->data, dbmfp->pgcookie->size);
            mfp->pgcookie_len = dbmfp->pgcookie->size;
      }

      if ((ret =
          __mutex_alloc(dbenv, MTX_MPOOLFILE_HANDLE, 0, &mfp->mutex)) != 0)
            goto err;

      /*
       * Prepend the MPOOLFILE to the list of MPOOLFILE's.
       */
      MPOOL_SYSTEM_LOCK(dbenv);
      SH_TAILQ_INSERT_HEAD(&mp->mpfq, mfp, q, __mpoolfile);
      MPOOL_SYSTEM_UNLOCK(dbenv);

have_mfp:
      /*
       * We need to verify that all handles open a file either durable or not
       * durable.  This needs to be cross process and cross sub-databases, so
       * mpool is the place to do it.
       */
      if (!LF_ISSET(DB_DURABLE_UNKNOWN | DB_RDONLY)) {
            if (F_ISSET(mfp, MP_DURABLE_UNKNOWN)) {
                  if (LF_ISSET(MP_NOT_DURABLE))
                        F_SET(mfp, MP_NOT_DURABLE);
                  F_CLR(mfp, MP_DURABLE_UNKNOWN);
            } else if (!LF_ISSET(DB_TXN_NOT_DURABLE) !=
                !F_ISSET(mfp, MP_NOT_DURABLE)) {
                  __db_err(dbenv,
           "Cannot open DURABLE and NOT DURABLE handles in the same file");
                  ret = EINVAL;
                  goto err;
            }
      }
      /*
       * All paths to here have initialized the mfp variable to reference
       * the selected (or allocated) MPOOLFILE.
       */
      dbmfp->mfp = mfp;

      /*
       * Check to see if we can mmap the file.  If a file:
       *    + isn't temporary
       *    + is read-only
       *    + doesn't require any pgin/pgout support
       *    + the DB_NOMMAP flag wasn't set (in either the file open or
       *      the environment in which it was opened)
       *    + and is less than mp_mmapsize bytes in size
       *
       * we can mmap it instead of reading/writing buffers.  Don't do error
       * checking based on the mmap call failure.  We want to do normal I/O
       * on the file if the reason we failed was because the file was on an
       * NFS mounted partition, and we can fail in buffer I/O just as easily
       * as here.
       *
       * We'd like to test to see if the file is too big to mmap.  Since we
       * don't know what size or type off_t's or size_t's are, or the largest
       * unsigned integral type is, or what random insanity the local C
       * compiler will perpetrate, doing the comparison in a portable way is
       * flatly impossible.  Hope that mmap fails if the file is too large.
       */
#define     DB_MAXMMAPSIZE    (10 * 1024 * 1024)      /* 10 MB. */
      if (F_ISSET(mfp, MP_CAN_MMAP)) {
            maxmap = dbenv->mp_mmapsize == 0 ?
                DB_MAXMMAPSIZE : dbenv->mp_mmapsize;
            if (path == NULL ||
                FLD_ISSET(dbmfp->config_flags, DB_MPOOL_NOFILE))
                  F_CLR(mfp, MP_CAN_MMAP);
            else if (!F_ISSET(dbmfp, MP_READONLY))
                  F_CLR(mfp, MP_CAN_MMAP);
            else if (dbmfp->ftype != 0)
                  F_CLR(mfp, MP_CAN_MMAP);
            else if (LF_ISSET(DB_NOMMAP) || F_ISSET(dbenv, DB_ENV_NOMMAP))
                  F_CLR(mfp, MP_CAN_MMAP);
            else {
                  MPOOL_SYSTEM_LOCK(dbenv);
                  maxmap = mp->mp_mmapsize == 0 ?
                      DB_MAXMMAPSIZE : mp->mp_mmapsize;
                  MPOOL_SYSTEM_UNLOCK(dbenv);
                  if (mbytes > maxmap / MEGABYTE ||
                      (mbytes == maxmap / MEGABYTE &&
                      bytes >= maxmap % MEGABYTE))
                        F_CLR(mfp, MP_CAN_MMAP);
            }

            dbmfp->addr = NULL;
            if (F_ISSET(mfp, MP_CAN_MMAP)) {
                  dbmfp->len = (size_t)mbytes * MEGABYTE + bytes;
                  if (__os_mapfile(dbenv, rpath,
                      dbmfp->fhp, dbmfp->len, 1, &dbmfp->addr) != 0) {
                        dbmfp->addr = NULL;
                        F_CLR(mfp, MP_CAN_MMAP);
                  }
            }
      }

      F_SET(dbmfp, MP_OPEN_CALLED);

      /*
       * Share the underlying file descriptor if that's possible.
       *
       * Add the file to the process' list of DB_MPOOLFILEs.
       */
      MUTEX_LOCK(dbenv, dbmp->mutex);

      if (dbmfp->fhp != NULL)
            for (tmp_dbmfp = TAILQ_FIRST(&dbmp->dbmfq);
                tmp_dbmfp != NULL; tmp_dbmfp = TAILQ_NEXT(tmp_dbmfp, q))
                  if (dbmfp->mfp == tmp_dbmfp->mfp &&
                      (F_ISSET(dbmfp, MP_READONLY) ||
                      !F_ISSET(tmp_dbmfp, MP_READONLY))) {
                        __mutex_free(dbenv, &dbmfp->fhp->mtx_fh);
                        (void)__os_closehandle(dbenv, dbmfp->fhp);
                        ++tmp_dbmfp->fhp->ref;
                        dbmfp->fhp = tmp_dbmfp->fhp;
                        break;
                  }

      TAILQ_INSERT_TAIL(&dbmp->dbmfq, dbmfp, q);

      MUTEX_UNLOCK(dbenv, dbmp->mutex);

      if (0) {
err:        if (refinc) {
                  /*
                   * If mpf_cnt goes to zero here and unlink_on_close is
                   * set, then we missed the last close, but there was an
                   * error trying to open the file, so we probably cannot
                   * unlink it anyway.
                   */
                  MUTEX_LOCK(dbenv, mfp->mutex);
                  --mfp->mpf_cnt;
                  MUTEX_UNLOCK(dbenv, mfp->mutex);
            }

      }
      if (rpath != NULL)
            __os_free(dbenv, rpath);
      return (ret);
}

/*
 * memp_fclose_pp --
 *    DB_MPOOLFILE->close pre/post processing.
 *
 * PUBLIC: int __memp_fclose_pp __P((DB_MPOOLFILE *, u_int32_t));
 */
int
__memp_fclose_pp(dbmfp, flags)
      DB_MPOOLFILE *dbmfp;
      u_int32_t flags;
{
      DB_ENV *dbenv;
      DB_THREAD_INFO *ip;
      int ret;

      dbenv = dbmfp->dbenv;

      /*
       * Validate arguments, but as a handle destructor, we can't fail.
       *
       * !!!
       * DB_MPOOL_DISCARD: Undocumented flag: DB private.
       */
      (void)__db_fchk(dbenv, "DB_MPOOLFILE->close", flags, DB_MPOOL_DISCARD);

      ENV_ENTER(dbenv, ip);
      REPLICATION_WRAP(dbenv, (__memp_fclose(dbmfp, flags)), ret);
      ENV_LEAVE(dbenv, ip);
      return (ret);
}

/*
 * __memp_fclose --
 *    DB_MPOOLFILE->close.
 *
 * PUBLIC: int __memp_fclose __P((DB_MPOOLFILE *, u_int32_t));
 */
int
__memp_fclose(dbmfp, flags)
      DB_MPOOLFILE *dbmfp;
      u_int32_t flags;
{
      DB_ENV *dbenv;
      DB_MPOOL *dbmp;
      MPOOLFILE *mfp;
      char *rpath;
      u_int32_t ref;
      int deleted, ret, t_ret;

      dbenv = dbmfp->dbenv;
      dbmp = dbenv->mp_handle;
      ret = 0;

      /*
       * Remove the DB_MPOOLFILE from the process' list.
       *
       * It's possible the underlying mpool cache may never have been created.
       * In that case, all we have is a structure, discard it.
       *
       * It's possible the DB_MPOOLFILE was never added to the DB_MPOOLFILE
       * file list, check the MP_OPEN_CALLED flag to be sure.
       */
      if (dbmp == NULL)
            goto done;

      MUTEX_LOCK(dbenv, dbmp->mutex);

      DB_ASSERT(dbmfp->ref >= 1);
      if ((ref = --dbmfp->ref) == 0 && F_ISSET(dbmfp, MP_OPEN_CALLED))
            TAILQ_REMOVE(&dbmp->dbmfq, dbmfp, q);

      /*
       * Decrement the file descriptor's ref count -- if we're the last ref,
       * we'll discard the file descriptor.
       */
      if (ref == 0 && dbmfp->fhp != NULL && --dbmfp->fhp->ref > 0)
            dbmfp->fhp = NULL;
      MUTEX_UNLOCK(dbenv, dbmp->mutex);
      if (ref != 0)
            return (0);

      /* Complain if pinned blocks never returned. */
      if (dbmfp->pinref != 0) {
            __db_err(dbenv, "%s: close: %lu blocks left pinned",
                __memp_fn(dbmfp), (u_long)dbmfp->pinref);
            ret = __db_panic(dbenv, DB_RUNRECOVERY);
      }

      /* Discard any mmap information. */
      if (dbmfp->addr != NULL &&
          (ret = __os_unmapfile(dbenv, dbmfp->addr, dbmfp->len)) != 0)
            __db_err(dbenv, "%s: %s", __memp_fn(dbmfp), db_strerror(ret));

      /*
       * Close the file and discard the descriptor structure; temporary
       * files may not yet have been created.
       */
      if (dbmfp->fhp != NULL) {
            if ((t_ret =
                __mutex_free(dbenv, &dbmfp->fhp->mtx_fh)) != 0 && ret == 0)
                  ret = t_ret;
            if ((t_ret = __os_closehandle(dbenv, dbmfp->fhp)) != 0) {
                  __db_err(dbenv, "%s: %s",
                      __memp_fn(dbmfp), db_strerror(t_ret));
                  if (ret == 0)
                        ret = t_ret;
            }
            dbmfp->fhp = NULL;
      }

      /*
       * Discard our reference on the underlying MPOOLFILE, and close it
       * if it's no longer useful to anyone.  It possible the open of the
       * file never happened or wasn't successful, in which case, mpf will
       * be NULL and MP_OPEN_CALLED will not be set.
       */
      mfp = dbmfp->mfp;
      DB_ASSERT((F_ISSET(dbmfp, MP_OPEN_CALLED) && mfp != NULL) ||
          (!F_ISSET(dbmfp, MP_OPEN_CALLED) && mfp == NULL));
      if (!F_ISSET(dbmfp, MP_OPEN_CALLED))
            goto done;

      /*
       * If it's a temp file, all outstanding references belong to unflushed
       * buffers.  (A temp file can only be referenced by one DB_MPOOLFILE).
       * We don't care about preserving any of those buffers, so mark the
       * MPOOLFILE as dead so that even the dirty ones just get discarded
       * when we try to flush them.
       */
      deleted = 0;
      MUTEX_LOCK(dbenv, mfp->mutex);
      if (--mfp->mpf_cnt == 0 || LF_ISSET(DB_MPOOL_DISCARD)) {
            if (LF_ISSET(DB_MPOOL_DISCARD) ||
                F_ISSET(mfp, MP_TEMP) || mfp->unlink_on_close) {
                  mfp->deadfile = 1;
            }
            if (mfp->unlink_on_close) {
                  if ((t_ret = __db_appname(dbmp->dbenv,
                      DB_APP_DATA, R_ADDR(dbmp->reginfo,
                      mfp->path_off), 0, NULL, &rpath)) != 0 && ret == 0)
                        ret = t_ret;
                  if (t_ret == 0) {
                        if ((t_ret = __os_unlink(
                            dbmp->dbenv, rpath)) != 0 && ret == 0)
                              ret = t_ret;
                        __os_free(dbenv, rpath);
                  }
            }
            if (mfp->block_cnt == 0) {
                  if ((t_ret =
                      __memp_mf_discard(dbmp, mfp)) != 0 && ret == 0)
                        ret = t_ret;
                  deleted = 1;
            }
      }
      if (deleted == 0)
            MUTEX_UNLOCK(dbenv, mfp->mutex);

done: /* Discard the DB_MPOOLFILE structure. */
      if (dbmfp->pgcookie != NULL) {
            __os_free(dbenv, dbmfp->pgcookie->data);
            __os_free(dbenv, dbmfp->pgcookie);
      }
      __os_free(dbenv, dbmfp);

      return (ret);
}

/*
 * __memp_mf_discard --
 *    Discard an MPOOLFILE.
 *
 * PUBLIC: int __memp_mf_discard __P((DB_MPOOL *, MPOOLFILE *));
 */
int
__memp_mf_discard(dbmp, mfp)
      DB_MPOOL *dbmp;
      MPOOLFILE *mfp;
{
      DB_ENV *dbenv;
      DB_MPOOL_STAT *sp;
      MPOOL *mp;
      int need_sync, ret, t_ret;

      dbenv = dbmp->dbenv;
      mp = dbmp->reginfo[0].primary;
      ret = 0;

      /*
       * Expects caller to be holding the MPOOLFILE mutex.
       *
       * When discarding a file, we have to flush writes from it to disk.
       * The scenario is that dirty buffers from this file need to be
       * flushed to satisfy a future checkpoint, but when the checkpoint
       * calls mpool sync, the sync code won't know anything about them.
       * Ignore files not written, discarded, or only temporary.
       */
      need_sync =
         mfp->file_written && !mfp->deadfile && !F_ISSET(mfp, MP_TEMP);

      /*
       * We have to release the MPOOLFILE mutex before acquiring the region
       * mutex so we don't deadlock.  Make sure nobody ever looks at this
       * structure again.
       */
      mfp->deadfile = 1;

      /* Discard the mutex we're holding and return it too the pool. */
      MUTEX_UNLOCK(dbenv, mfp->mutex);
      if ((t_ret = __mutex_free(dbenv, &mfp->mutex)) != 0 && ret == 0)
            ret = t_ret;

      /* Lock the region and delete from the list of MPOOLFILEs. */
      MPOOL_SYSTEM_LOCK(dbenv);
      SH_TAILQ_REMOVE(&mp->mpfq, mfp, q, __mpoolfile);

      if (need_sync &&
          (t_ret = __memp_mf_sync(dbmp, mfp, 1)) != 0 && ret == 0)
            ret = t_ret;

      /* Copy the statistics into the region. */
      sp = &mp->stat;
      sp->st_cache_hit += mfp->stat.st_cache_hit;
      sp->st_cache_miss += mfp->stat.st_cache_miss;
      sp->st_map += mfp->stat.st_map;
      sp->st_page_create += mfp->stat.st_page_create;
      sp->st_page_in += mfp->stat.st_page_in;
      sp->st_page_out += mfp->stat.st_page_out;

      /* Free the space. */
      if (mfp->path_off != 0)
            __db_shalloc_free(&dbmp->reginfo[0],
                R_ADDR(dbmp->reginfo, mfp->path_off));
      if (mfp->fileid_off != 0)
            __db_shalloc_free(&dbmp->reginfo[0],
                R_ADDR(dbmp->reginfo, mfp->fileid_off));
      if (mfp->pgcookie_off != 0)
            __db_shalloc_free(&dbmp->reginfo[0],
                R_ADDR(dbmp->reginfo, mfp->pgcookie_off));
      __db_shalloc_free(&dbmp->reginfo[0], mfp);

      MPOOL_SYSTEM_UNLOCK(dbenv);

      return (ret);
}

/*
 * __memp_inmemlist --
 *    Return a list of the named in-memory databases.
 *
 * PUBLIC: int __memp_inmemlist __P((DB_ENV *, char ***, int *));
 */
int
__memp_inmemlist(dbenv, namesp, cntp)
      DB_ENV *dbenv;
      char ***namesp;
      int *cntp;
{
      DB_MPOOL *dbmp;
      MPOOL *mp;
      MPOOLFILE *mfp;

      int arraysz, cnt, ret;
      char **names;

      names = NULL;
      dbmp = dbenv->mp_handle;
      mp = dbmp->reginfo[0].primary;

      arraysz = cnt = 0;
      MPOOL_SYSTEM_LOCK(dbenv);
      for (mfp = SH_TAILQ_FIRST(&mp->mpfq, __mpoolfile);
          mfp != NULL; mfp = SH_TAILQ_NEXT(mfp, q, __mpoolfile)) {
            /* Skip dead files and temporary files. */
            if (mfp->deadfile || F_ISSET(mfp, MP_TEMP))
                  continue;

            /* Skip entries that allow files. */
            if (!mfp->no_backing_file)
                  continue;

            /* We found one. */
            if (cnt >= arraysz) {
                  arraysz += 100;
                  if ((ret = __os_realloc(dbenv,
                      (u_int)arraysz * sizeof(names[0]), &names)) != 0)
                        goto nomem;
            }
            if ((ret = __os_strdup(dbenv,
                R_ADDR(dbmp->reginfo, mfp->path_off), &names[cnt])) != 0)
                  goto nomem;

            cnt++;
      }
      MPOOL_SYSTEM_UNLOCK(dbenv);
      *namesp = names;
      *cntp = cnt;
      return (0);

nomem:      MPOOL_SYSTEM_UNLOCK(dbenv);
      if (names != NULL) {
            while (--cnt >= 0)
                  __os_free(dbenv, names[cnt]);
            __os_free(dbenv, names);
      }

      /* Make sure we don't return any garbage. */
      *cntp = 0;
      *namesp = NULL;
      return (ret);
}

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