tdb: introduce tdb->hdr_ofs

[Samba.git] / lib / tdb / common / open.c

 /*
   Unix SMB/CIFS implementation.

   trivial database library

   Copyright (C) Andrew Tridgell              1999-2005
   Copyright (C) Paul `Rusty' Russell              2000
   Copyright (C) Jeremy Allison                    2000-2003

     ** NOTE! The following LGPL license applies to the tdb
     ** library. This does NOT imply that all of Samba is released
     ** under the LGPL

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 3 of the License, or (at your option) any later version.

   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/

#include "tdb_private.h"

/* all contexts, to ensure no double-opens (fcntl locks don't nest!) */
static struct tdb_context *tdbs = NULL;

/* We use two hashes to double-check they're using the right hash function. */
void tdb_header_hash(struct tdb_context *tdb,
                     uint32_t *magic1_hash, uint32_t *magic2_hash)
{
        TDB_DATA hash_key;
        uint32_t tdb_magic = TDB_MAGIC;

        hash_key.dptr = discard_const_p(unsigned char, TDB_MAGIC_FOOD);
        hash_key.dsize = sizeof(TDB_MAGIC_FOOD);
        *magic1_hash = tdb->hash_fn(&hash_key);

        hash_key.dptr = (unsigned char *)CONVERT(tdb_magic);
        hash_key.dsize = sizeof(tdb_magic);
        *magic2_hash = tdb->hash_fn(&hash_key);

        /* Make sure at least one hash is non-zero! */
        if (*magic1_hash == 0 && *magic2_hash == 0)
                *magic1_hash = 1;
}

/* initialise a new database with a specified hash size */
static int tdb_new_database(struct tdb_context *tdb, struct tdb_header *header,
                            int hash_size)
{
        struct tdb_header *newdb;
        size_t size;
        int ret = -1;

        /* We make it up in memory, then write it out if not internal */
        size = sizeof(struct tdb_header) + (hash_size+1)*sizeof(tdb_off_t);
        if (!(newdb = (struct tdb_header *)calloc(size, 1))) {
                tdb->ecode = TDB_ERR_OOM;
                return -1;
        }

        /* Fill in the header */
        newdb->version = TDB_VERSION;
        newdb->hash_size = hash_size;

        tdb_header_hash(tdb, &newdb->magic1_hash, &newdb->magic2_hash);

        /* Make sure older tdbs (which don't check the magic hash fields)
         * will refuse to open this TDB. */
        if (tdb->flags & TDB_INCOMPATIBLE_HASH)
                newdb->rwlocks = TDB_HASH_RWLOCK_MAGIC;

        /*
         * If we have any features we add the FEATURE_FLAG_MAGIC, overwriting the
         * TDB_HASH_RWLOCK_MAGIC above.
         */
        if (newdb->feature_flags != 0) {
                newdb->rwlocks = TDB_FEATURE_FLAG_MAGIC;
        }

        /*
         * It's required for some following code pathes
         * to have the fields on 'tdb' up-to-date.
         */
        tdb->feature_flags = newdb->feature_flags;

        if (tdb->flags & TDB_INTERNAL) {
                tdb->map_size = size;
                tdb->map_ptr = (char *)newdb;
                memcpy(header, newdb, sizeof(*header));
                /* Convert the `ondisk' version if asked. */
                CONVERT(*newdb);
                return 0;
        }
        if (lseek(tdb->fd, 0, SEEK_SET) == -1)
                goto fail;

        if (ftruncate(tdb->fd, 0) == -1)
                goto fail;

        /* This creates an endian-converted header, as if read from disk */
        CONVERT(*newdb);
        memcpy(header, newdb, sizeof(*header));
        /* Don't endian-convert the magic food! */
        memcpy(newdb->magic_food, TDB_MAGIC_FOOD, strlen(TDB_MAGIC_FOOD)+1);

        if (!tdb_write_all(tdb->fd, newdb, size))
                goto fail;

        ret = 0;
  fail:
        SAFE_FREE(newdb);
        return ret;
}



static int tdb_already_open(dev_t device,
                            ino_t ino)
{
        struct tdb_context *i;

        for (i = tdbs; i; i = i->next) {
                if (i->device == device && i->inode == ino) {
                        return 1;
                }
        }

        return 0;
}

/* open the database, creating it if necessary

   The open_flags and mode are passed straight to the open call on the
   database file. A flags value of O_WRONLY is invalid. The hash size
   is advisory, use zero for a default value.

   Return is NULL on error, in which case errno is also set.  Don't
   try to call tdb_error or tdb_errname, just do strerror(errno).

   @param name may be NULL for internal databases. */
_PUBLIC_ struct tdb_context *tdb_open(const char *name, int hash_size, int tdb_flags,
                      int open_flags, mode_t mode)
{
        return tdb_open_ex(name, hash_size, tdb_flags, open_flags, mode, NULL, NULL);
}

/* a default logging function */
static void null_log_fn(struct tdb_context *tdb, enum tdb_debug_level level, const char *fmt, ...) PRINTF_ATTRIBUTE(3, 4);
static void null_log_fn(struct tdb_context *tdb, enum tdb_debug_level level, const char *fmt, ...)
{
}

static bool check_header_hash(struct tdb_context *tdb,
                              struct tdb_header *header,
                              bool default_hash, uint32_t *m1, uint32_t *m2)
{
        tdb_header_hash(tdb, m1, m2);
        if (header->magic1_hash == *m1 &&
            header->magic2_hash == *m2) {
                return true;
        }

        /* If they explicitly set a hash, always respect it. */
        if (!default_hash)
                return false;

        /* Otherwise, try the other inbuilt hash. */
        if (tdb->hash_fn == tdb_old_hash)
                tdb->hash_fn = tdb_jenkins_hash;
        else
                tdb->hash_fn = tdb_old_hash;
        return check_header_hash(tdb, header, false, m1, m2);
}

_PUBLIC_ struct tdb_context *tdb_open_ex(const char *name, int hash_size, int tdb_flags,
                                int open_flags, mode_t mode,
                                const struct tdb_logging_context *log_ctx,
                                tdb_hash_func hash_fn)
{
        int orig_errno = errno;
        struct tdb_header header;
        struct tdb_context *tdb;
        struct stat st;
        int rev = 0, locked = 0;
        unsigned char *vp;
        uint32_t vertest;
        unsigned v;
        const char *hash_alg;
        uint32_t magic1, magic2;
        int ret;

        ZERO_STRUCT(header);

        if (!(tdb = (struct tdb_context *)calloc(1, sizeof *tdb))) {
                /* Can't log this */
                errno = ENOMEM;
                goto fail;
        }
        tdb_io_init(tdb);

        if (tdb_flags & TDB_INTERNAL) {
                tdb_flags |= TDB_INCOMPATIBLE_HASH;
        }

        tdb->fd = -1;
#ifdef TDB_TRACE
        tdb->tracefd = -1;
#endif
        tdb->name = NULL;
        tdb->map_ptr = NULL;
        tdb->flags = tdb_flags;
        tdb->open_flags = open_flags;
        if (log_ctx) {
                tdb->log = *log_ctx;
        } else {
                tdb->log.log_fn = null_log_fn;
                tdb->log.log_private = NULL;
        }

        if (name == NULL && (tdb_flags & TDB_INTERNAL)) {
                name = "__TDB_INTERNAL__";
        }

        if (name == NULL) {
                tdb->name = discard_const_p(char, "__NULL__");
                TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_open_ex: called with name == NULL\n"));
                tdb->name = NULL;
                errno = EINVAL;
                goto fail;
        }

        /* now make a copy of the name, as the caller memory might go away */
        if (!(tdb->name = (char *)strdup(name))) {
                /*
                 * set the name as the given string, so that tdb_name() will
                 * work in case of an error.
                 */
                tdb->name = discard_const_p(char, name);
                TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_open_ex: can't strdup(%s)\n",
                         name));
                tdb->name = NULL;
                errno = ENOMEM;
                goto fail;
        }

        if (hash_fn) {
                tdb->hash_fn = hash_fn;
                hash_alg = "the user defined";
        } else {
                /* This controls what we use when creating a tdb. */
                if (tdb->flags & TDB_INCOMPATIBLE_HASH) {
                        tdb->hash_fn = tdb_jenkins_hash;
                } else {
                        tdb->hash_fn = tdb_old_hash;
                }
                hash_alg = "either default";
        }

        /* cache the page size */
        tdb->page_size = getpagesize();
        if (tdb->page_size <= 0) {
                tdb->page_size = 0x2000;
        }

        tdb->max_dead_records = (tdb_flags & TDB_VOLATILE) ? 5 : 0;

        if ((open_flags & O_ACCMODE) == O_WRONLY) {
                TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_open_ex: can't open tdb %s write-only\n",
                         name));
                errno = EINVAL;
                goto fail;
        }

        if (hash_size == 0)
                hash_size = DEFAULT_HASH_SIZE;
        if ((open_flags & O_ACCMODE) == O_RDONLY) {
                tdb->read_only = 1;
                /* read only databases don't do locking or clear if first */
                tdb->flags |= TDB_NOLOCK;
                tdb->flags &= ~TDB_CLEAR_IF_FIRST;
        }

        if ((tdb->flags & TDB_ALLOW_NESTING) &&
            (tdb->flags & TDB_DISALLOW_NESTING)) {
                tdb->ecode = TDB_ERR_NESTING;
                TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_open_ex: "
                        "allow_nesting and disallow_nesting are not allowed together!"));
                errno = EINVAL;
                goto fail;
        }

        if (getenv("TDB_NO_FSYNC")) {
                tdb->flags |= TDB_NOSYNC;
        }

        /*
         * TDB_ALLOW_NESTING is the default behavior.
         * Note: this may change in future versions!
         */
        if (!(tdb->flags & TDB_DISALLOW_NESTING)) {
                tdb->flags |= TDB_ALLOW_NESTING;
        }

        /* internal databases don't mmap or lock, and start off cleared */
        if (tdb->flags & TDB_INTERNAL) {
                tdb->flags |= (TDB_NOLOCK | TDB_NOMMAP);
                tdb->flags &= ~TDB_CLEAR_IF_FIRST;
                if (tdb_new_database(tdb, &header, hash_size) != 0) {
                        TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_open_ex: tdb_new_database failed!"));
                        goto fail;
                }
                tdb->hash_size = hash_size;
                goto internal;
        }

        if ((tdb->fd = open(name, open_flags, mode)) == -1) {
                TDB_LOG((tdb, TDB_DEBUG_WARNING, "tdb_open_ex: could not open file %s: %s\n",
                         name, strerror(errno)));
                goto fail;      /* errno set by open(2) */
        }

        /* on exec, don't inherit the fd */
        v = fcntl(tdb->fd, F_GETFD, 0);
        fcntl(tdb->fd, F_SETFD, v | FD_CLOEXEC);

        /* ensure there is only one process initialising at once */
        if (tdb_nest_lock(tdb, OPEN_LOCK, F_WRLCK, TDB_LOCK_WAIT) == -1) {
                TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_open_ex: failed to get open lock on %s: %s\n",
                         name, strerror(errno)));
                goto fail;      /* errno set by tdb_brlock */
        }

        /* we need to zero database if we are the only one with it open */
        if ((tdb_flags & TDB_CLEAR_IF_FIRST) &&
            (!tdb->read_only) &&
            (locked = (tdb_nest_lock(tdb, ACTIVE_LOCK, F_WRLCK, TDB_LOCK_NOWAIT|TDB_LOCK_PROBE) == 0))) {
                ret = tdb_brlock(tdb, F_WRLCK, FREELIST_TOP, 0,
                                 TDB_LOCK_WAIT);
                if (ret == -1) {
                        TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_open_ex: "
                                 "tdb_brlock failed for %s: %s\n",
                                 name, strerror(errno)));
                        goto fail;
                }
                ret = tdb_new_database(tdb, &header, hash_size);
                if (ret == -1) {
                        TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_open_ex: "
                                 "tdb_new_database failed for %s: %s\n",
                                 name, strerror(errno)));
                        tdb_unlockall(tdb);
                        goto fail;
                }
                ret = tdb_brunlock(tdb, F_WRLCK, FREELIST_TOP, 0);
                if (ret == -1) {
                        TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_open_ex: "
                                 "tdb_unlockall failed for %s: %s\n",
                                 name, strerror(errno)));
                        goto fail;
                }
                ret = lseek(tdb->fd, 0, SEEK_SET);
                if (ret == -1) {
                        TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_open_ex: "
                                 "lseek failed for %s: %s\n",
                                 name, strerror(errno)));
                        goto fail;
                }
        }

        errno = 0;
        if (read(tdb->fd, &header, sizeof(header)) != sizeof(header)
            || strcmp(header.magic_food, TDB_MAGIC_FOOD) != 0) {
                if (!(open_flags & O_CREAT) ||
                    tdb_new_database(tdb, &header, hash_size) == -1) {
                        if (errno == 0) {
                                errno = EIO; /* ie bad format or something */
                        }
                        goto fail;
                }
                rev = (tdb->flags & TDB_CONVERT);
        } else if (header.version != TDB_VERSION
                   && !(rev = (header.version==TDB_BYTEREV(TDB_VERSION)))) {
                /* wrong version */
                errno = EIO;
                goto fail;
        }
        vp = (unsigned char *)&header.version;
        vertest = (((uint32_t)vp[0]) << 24) | (((uint32_t)vp[1]) << 16) |
                  (((uint32_t)vp[2]) << 8) | (uint32_t)vp[3];
        tdb->flags |= (vertest==TDB_VERSION) ? TDB_BIGENDIAN : 0;
        if (!rev)
                tdb->flags &= ~TDB_CONVERT;
        else {
                tdb->flags |= TDB_CONVERT;
                tdb_convert(&header, sizeof(header));
        }

        /*
         * We only use st.st_dev and st.st_ino from the raw fstat()
         * call, everything else needs to use tdb_fstat() in order
         * to skip tdb->hdr_ofs!
         */
        if (fstat(tdb->fd, &st) == -1) {
                goto fail;
        }
        tdb->device = st.st_dev;
        tdb->inode = st.st_ino;
        ZERO_STRUCT(st);

        if (header.rwlocks != 0 &&
            header.rwlocks != TDB_FEATURE_FLAG_MAGIC &&
            header.rwlocks != TDB_HASH_RWLOCK_MAGIC) {
                TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_open_ex: spinlocks no longer supported\n"));
                errno = ENOSYS;
                goto fail;
        }
        tdb->hash_size = header.hash_size;

        if (header.rwlocks == TDB_FEATURE_FLAG_MAGIC) {
                tdb->feature_flags = header.feature_flags;
        }

        if (tdb->feature_flags & ~TDB_SUPPORTED_FEATURE_FLAGS) {
                TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_open_ex: unsupported "
                         "features in tdb %s: 0x%08x (supported: 0x%08x)\n",
                         name, (unsigned)tdb->feature_flags,
                         (unsigned)TDB_SUPPORTED_FEATURE_FLAGS));
                errno = ENOSYS;
                goto fail;
        }

        if ((header.magic1_hash == 0) && (header.magic2_hash == 0)) {
                /* older TDB without magic hash references */
                tdb->hash_fn = tdb_old_hash;
        } else if (!check_header_hash(tdb, &header, !hash_fn,
                                      &magic1, &magic2)) {
                TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_open_ex: "
                         "%s was not created with %s hash function we are using\n"
                         "magic1_hash[0x%08X %s 0x%08X] "
                         "magic2_hash[0x%08X %s 0x%08X]\n",
                         name, hash_alg,
                         header.magic1_hash,
                         (header.magic1_hash == magic1) ? "==" : "!=",
                         magic1,
                         header.magic2_hash,
                         (header.magic2_hash == magic2) ? "==" : "!=",
                         magic2));
                errno = EINVAL;
                goto fail;
        }

        /* Is it already in the open list?  If so, fail. */
        if (tdb_already_open(tdb->device, tdb->inode)) {
                TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_open_ex: "
                         "%s (%d,%d) is already open in this process\n",
                         name, (int)tdb->device, (int)tdb->inode));
                errno = EBUSY;
                goto fail;
        }

        /*
         * We had tdb_mmap(tdb) here before,
         * but we need to use tdb_fstat(),
         * which is triggered from tdb_oob() before calling tdb_mmap().
         * As this skips tdb->hdr_ofs.
         */
        tdb->map_size = 0;
        ret = tdb->methods->tdb_oob(tdb, 0, 1, 0);
        if (ret == -1) {
                errno = EIO;
                goto fail;
        }

        if (locked) {
                if (tdb_nest_unlock(tdb, ACTIVE_LOCK, F_WRLCK, false) == -1) {
                        TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_open_ex: "
                                 "failed to release ACTIVE_LOCK on %s: %s\n",
                                 name, strerror(errno)));
                        goto fail;
                }

        }

        /* We always need to do this if the CLEAR_IF_FIRST flag is set, even if
           we didn't get the initial exclusive lock as we need to let all other
           users know we're using it. */

        if (tdb_flags & TDB_CLEAR_IF_FIRST) {
                /* leave this lock in place to indicate it's in use */
                if (tdb_nest_lock(tdb, ACTIVE_LOCK, F_RDLCK, TDB_LOCK_WAIT) == -1) {
                        goto fail;
                }
        }

        /* if needed, run recovery */
        if (tdb_transaction_recover(tdb) == -1) {
                goto fail;
        }

#ifdef TDB_TRACE
        {
                char tracefile[strlen(name) + 32];

                snprintf(tracefile, sizeof(tracefile),
                         "%s.trace.%li", name, (long)getpid());
                tdb->tracefd = open(tracefile, O_WRONLY|O_CREAT|O_EXCL, 0600);
                if (tdb->tracefd >= 0) {
                        tdb_enable_seqnum(tdb);
                        tdb_trace_open(tdb, "tdb_open", hash_size, tdb_flags,
                                       open_flags);
                } else
                        TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_open_ex: failed to open trace file %s!\n", tracefile));
        }
#endif

 internal:
        /* Internal (memory-only) databases skip all the code above to
         * do with disk files, and resume here by releasing their
         * open lock and hooking into the active list. */
        if (tdb_nest_unlock(tdb, OPEN_LOCK, F_WRLCK, false) == -1) {
                goto fail;
        }
        tdb->next = tdbs;
        tdbs = tdb;
        errno = orig_errno;
        return tdb;

 fail:
        { int save_errno = errno;

        if (!tdb)
                return NULL;

#ifdef TDB_TRACE
        close(tdb->tracefd);
#endif
        if (tdb->map_ptr) {
                if (tdb->flags & TDB_INTERNAL)
                        SAFE_FREE(tdb->map_ptr);
                else
                        tdb_munmap(tdb);
        }
        if (tdb->fd != -1)
                if (close(tdb->fd) != 0)
                        TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_open_ex: failed to close tdb->fd on error!\n"));
        SAFE_FREE(tdb->lockrecs);
        SAFE_FREE(tdb->name);
        SAFE_FREE(tdb);
        errno = save_errno;
        return NULL;
        }
}

/*
 * Set the maximum number of dead records per hash chain
 */

_PUBLIC_ void tdb_set_max_dead(struct tdb_context *tdb, int max_dead)
{
        tdb->max_dead_records = max_dead;
}

/**
 * Close a database.
 *
 * @returns -1 for error; 0 for success.
 **/
_PUBLIC_ int tdb_close(struct tdb_context *tdb)
{
        struct tdb_context **i;
        int ret = 0;

        if (tdb->transaction) {
                tdb_transaction_cancel(tdb);
        }
        tdb_trace(tdb, "tdb_close");

        if (tdb->map_ptr) {
                if (tdb->flags & TDB_INTERNAL)
                        SAFE_FREE(tdb->map_ptr);
                else
                        tdb_munmap(tdb);
        }
        SAFE_FREE(tdb->name);
        if (tdb->fd != -1) {
                ret = close(tdb->fd);
                tdb->fd = -1;
        }
        SAFE_FREE(tdb->lockrecs);

        /* Remove from contexts list */
        for (i = &tdbs; *i; i = &(*i)->next) {
                if (*i == tdb) {
                        *i = tdb->next;
                        break;
                }
        }

#ifdef TDB_TRACE
        close(tdb->tracefd);
#endif
        memset(tdb, 0, sizeof(*tdb));
        SAFE_FREE(tdb);

        return ret;
}

/* register a loging function */
_PUBLIC_ void tdb_set_logging_function(struct tdb_context *tdb,
                                       const struct tdb_logging_context *log_ctx)
{
        tdb->log = *log_ctx;
}

_PUBLIC_ void *tdb_get_logging_private(struct tdb_context *tdb)
{
        return tdb->log.log_private;
}

static int tdb_reopen_internal(struct tdb_context *tdb, bool active_lock)
{
#if !defined(LIBREPLACE_PREAD_NOT_REPLACED) || \
        !defined(LIBREPLACE_PWRITE_NOT_REPLACED)
        struct stat st;
#endif

        if (tdb->flags & TDB_INTERNAL) {
                return 0; /* Nothing to do. */
        }

        if (tdb_have_extra_locks(tdb)) {
                TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_reopen: reopen not allowed with locks held\n"));
                goto fail;
        }

        if (tdb->transaction != 0) {
                TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_reopen: reopen not allowed inside a transaction\n"));
                goto fail;
        }

/* If we have real pread & pwrite, we can skip reopen. */
#if !defined(LIBREPLACE_PREAD_NOT_REPLACED) || \
        !defined(LIBREPLACE_PWRITE_NOT_REPLACED)
        if (tdb_munmap(tdb) != 0) {
                TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_reopen: munmap failed (%s)\n", strerror(errno)));
                goto fail;
        }
        if (close(tdb->fd) != 0)
                TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_reopen: WARNING closing tdb->fd failed!\n"));
        tdb->fd = open(tdb->name, tdb->open_flags & ~(O_CREAT|O_TRUNC), 0);
        if (tdb->fd == -1) {
                TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_reopen: open failed (%s)\n", strerror(errno)));
                goto fail;
        }
        /*
         * We only use st.st_dev and st.st_ino from the raw fstat()
         * call, everything else needs to use tdb_fstat() in order
         * to skip tdb->hdr_ofs!
         */
        if (fstat(tdb->fd, &st) != 0) {
                TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_reopen: fstat failed (%s)\n", strerror(errno)));
                goto fail;
        }
        if (st.st_ino != tdb->inode || st.st_dev != tdb->device) {
                TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_reopen: file dev/inode has changed!\n"));
                goto fail;
        }
        ZERO_STRUCT(st);

        /*
         * We had tdb_mmap(tdb) here before,
         * but we need to use tdb_fstat(),
         * which is triggered from tdb_oob() before calling tdb_mmap().
         * As this skips tdb->hdr_ofs.
         */
        tdb->map_size = 0;
        if (tdb->methods->tdb_oob(tdb, 0, 1, 0) != 0) {
                goto fail;
        }
#endif /* fake pread or pwrite */

        /* We may still think we hold the active lock. */
        tdb->num_lockrecs = 0;
        SAFE_FREE(tdb->lockrecs);
        tdb->lockrecs_array_length = 0;

        if (active_lock && tdb_nest_lock(tdb, ACTIVE_LOCK, F_RDLCK, TDB_LOCK_WAIT) == -1) {
                TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_reopen: failed to obtain active lock\n"));
                goto fail;
        }

        return 0;

fail:
        tdb_close(tdb);
        return -1;
}

/* reopen a tdb - this can be used after a fork to ensure that we have an independent
   seek pointer from our parent and to re-establish locks */
_PUBLIC_ int tdb_reopen(struct tdb_context *tdb)
{
        return tdb_reopen_internal(tdb, tdb->flags & TDB_CLEAR_IF_FIRST);
}

/* reopen all tdb's */
_PUBLIC_ int tdb_reopen_all(int parent_longlived)
{
        struct tdb_context *tdb;

        for (tdb=tdbs; tdb; tdb = tdb->next) {
                bool active_lock = (tdb->flags & TDB_CLEAR_IF_FIRST);

                /*
                 * If the parent is longlived (ie. a
                 * parent daemon architecture), we know
                 * it will keep it's active lock on a
                 * tdb opened with CLEAR_IF_FIRST. Thus
                 * for child processes we don't have to
                 * add an active lock. This is essential
                 * to improve performance on systems that
                 * keep POSIX locks as a non-scalable data
                 * structure in the kernel.
                 */
                if (parent_longlived) {
                        /* Ensure no clear-if-first. */
                        active_lock = false;
                }

                if (tdb_reopen_internal(tdb, active_lock) != 0)
                        return -1;
        }

        return 0;
}