Adding upstream version 1.47.0.upstream/1.47.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 4174 insertions, 0 deletions

diff --git a/lib/ext2fs/tdb.c b/lib/ext2fs/tdb.c
new file mode 100644
index 0000000..b07b291
--- /dev/null
+++ b/lib/ext2fs/tdb.c
@@ -0,0 +1,4174 @@
+/*
+URL: svn://svnanon.samba.org/samba/branches/SAMBA_4_0/source/lib/tdb/common
+Rev: 23590
+Last Changed Date: 2007-06-22 13:36:10 -0400 (Fri, 22 Jun 2007)
+*/
+ /*
+   trivial database library - standalone version
+
+   Copyright (C) Andrew Tridgell              1999-2005
+   Copyright (C) Jeremy Allison               2000-2006
+   Copyright (C) Paul `Rusty' Russell         2000
+
+     ** 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 2 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, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301  USA
+*/
+
+#ifdef CONFIG_STAND_ALONE
+#define HAVE_MMAP
+#define HAVE_STRDUP
+#define HAVE_SYS_MMAN_H
+#define HAVE_UTIME_H
+#define HAVE_UTIME
+#endif
+#ifndef __FreeBSD__
+#define _XOPEN_SOURCE 600
+#endif
+
+#include "config.h"
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdarg.h>
+#include <stddef.h>
+#include <errno.h>
+#include <string.h>
+#ifdef HAVE_SYS_SELECT_H
+#include <sys/select.h>
+#endif
+#include <sys/time.h>
+#include <sys/types.h>
+#include <time.h>
+#ifdef HAVE_UTIME_H
+#include <utime.h>
+#endif
+#include <sys/stat.h>
+#include <sys/file.h>
+#include <fcntl.h>
+
+#ifdef HAVE_SYS_MMAN_H
+#include <sys/mman.h>
+#endif
+
+#ifdef __GNUC__
+#define EXT2FS_ATTR(x) __attribute__(x)
+#else
+#define EXT2FS_ATTR(x)
+#endif
+
+#ifndef MAP_FILE
+#define MAP_FILE 0
+#endif
+
+#ifndef MAP_FAILED
+#define MAP_FAILED ((void *)-1)
+#endif
+
+#ifndef HAVE_STRDUP
+#define strdup rep_strdup
+static char *rep_strdup(const char *s)
+{
+	char *ret;
+	int length;
+
+	if (!s)
+		return NULL;
+	length = strlen(s);
+	ret = malloc(length + 1);
+	if (ret) {
+		strncpy(ret, s, length);
+		ret[length] = '\0';
+	}
+	return ret;
+}
+#endif
+
+#ifndef PRINTF_ATTRIBUTE
+#if (__GNUC__ >= 3) && (__GNUC_MINOR__ >= 1 )
+/** Use gcc attribute to check printf fns.  a1 is the 1-based index of
+ * the parameter containing the format, and a2 the index of the first
+ * argument. Note that some gcc 2.x versions don't handle this
+ * properly **/
+#define PRINTF_ATTRIBUTE(a1, a2) __attribute__ ((format (__printf__, a1, a2)))
+#else
+#define PRINTF_ATTRIBUTE(a1, a2)
+#endif
+#endif
+
+typedef int bool;
+
+#include "tdb.h"
+
+static TDB_DATA tdb_null;
+
+#ifndef u32
+#define u32 unsigned
+#endif
+
+typedef u32 tdb_len_t;
+typedef u32 tdb_off_t;
+
+#ifndef offsetof
+#define offsetof(t,f) ((unsigned int)&((t *)0)->f)
+#endif
+
+#define TDB_MAGIC_FOOD "TDB file\n"
+#define TDB_VERSION (0x26011967 + 6)
+#define TDB_MAGIC (0x26011999U)
+#define TDB_FREE_MAGIC (~TDB_MAGIC)
+#define TDB_DEAD_MAGIC (0xFEE1DEAD)
+#define TDB_RECOVERY_MAGIC (0xf53bc0e7U)
+#define TDB_ALIGNMENT 4
+#define MIN_REC_SIZE (2*sizeof(struct list_struct) + TDB_ALIGNMENT)
+#define DEFAULT_HASH_SIZE 131
+#define FREELIST_TOP (sizeof(struct tdb_header))
+#define TDB_ALIGN(x,a) (((x) + (a)-1) & ~((a)-1))
+#define TDB_BYTEREV(x) (((((x)&0xff)<<24)|((x)&0xFF00)<<8)|(((x)>>8)&0xFF00)|((x)>>24))
+#define TDB_DEAD(r) ((r)->magic == TDB_DEAD_MAGIC)
+#define TDB_BAD_MAGIC(r) ((r)->magic != TDB_MAGIC && !TDB_DEAD(r))
+#define TDB_HASH_TOP(hash) (FREELIST_TOP + (BUCKET(hash)+1)*sizeof(tdb_off_t))
+#define TDB_HASHTABLE_SIZE(tdb) ((tdb->header.hash_size+1)*sizeof(tdb_off_t))
+#define TDB_DATA_START(hash_size) TDB_HASH_TOP(hash_size-1)
+#define TDB_RECOVERY_HEAD offsetof(struct tdb_header, recovery_start)
+#define TDB_SEQNUM_OFS    offsetof(struct tdb_header, sequence_number)
+#define TDB_PAD_BYTE 0x42
+#define TDB_PAD_U32  0x42424242
+
+/* NB assumes there is a local variable called "tdb" that is the
+ * current context, also takes doubly-parenthesized print-style
+ * argument. */
+#define TDB_LOG(x) tdb->log.log_fn x
+
+/* lock offsets */
+#define GLOBAL_LOCK      0
+#define ACTIVE_LOCK      4
+#define TRANSACTION_LOCK 8
+
+/* free memory if the pointer is valid and zero the pointer */
+#ifndef SAFE_FREE
+#define SAFE_FREE(x) do { if ((x) != NULL) {free(x); (x)=NULL;} } while(0)
+#endif
+
+#define BUCKET(hash) ((hash) % tdb->header.hash_size)
+
+#define DOCONV() (tdb->flags & TDB_CONVERT)
+#define CONVERT(x) (DOCONV() ? tdb_convert(&x, sizeof(x)) : &x)
+
+
+/* the body of the database is made of one list_struct for the free space
+   plus a separate data list for each hash value */
+struct list_struct {
+	tdb_off_t next; /* offset of the next record in the list */
+	tdb_len_t rec_len; /* total byte length of record */
+	tdb_len_t key_len; /* byte length of key */
+	tdb_len_t data_len; /* byte length of data */
+	u32 full_hash; /* the full 32 bit hash of the key */
+	u32 magic;   /* try to catch errors */
+	/* the following union is implied:
+		union {
+			char record[rec_len];
+			struct {
+				char key[key_len];
+				char data[data_len];
+			}
+			u32 totalsize; (tailer)
+		}
+	*/
+};
+
+
+/* this is stored at the front of every database */
+struct tdb_header {
+	char magic_food[32]; /* for /etc/magic */
+	u32 version; /* version of the code */
+	u32 hash_size; /* number of hash entries */
+	tdb_off_t rwlocks; /* obsolete - kept to detect old formats */
+	tdb_off_t recovery_start; /* offset of transaction recovery region */
+	tdb_off_t sequence_number; /* used when TDB_SEQNUM is set */
+	tdb_off_t reserved[29];
+};
+
+struct tdb_lock_type {
+	int list;
+	u32 count;
+	u32 ltype;
+};
+
+struct tdb_traverse_lock {
+	struct tdb_traverse_lock *next;
+	u32 off;
+	u32 hash;
+	int lock_rw;
+};
+
+
+struct tdb_methods {
+	int (*tdb_read)(struct tdb_context *, tdb_off_t , void *, tdb_len_t , int );
+	int (*tdb_write)(struct tdb_context *, tdb_off_t, const void *, tdb_len_t);
+	void (*next_hash_chain)(struct tdb_context *, u32 *);
+	int (*tdb_oob)(struct tdb_context *, tdb_off_t , int );
+	int (*tdb_expand_file)(struct tdb_context *, tdb_off_t , tdb_off_t );
+	int (*tdb_brlock)(struct tdb_context *, tdb_off_t , int, int, int, size_t);
+};
+
+struct tdb_context {
+	char *name; /* the name of the database */
+	void *map_ptr; /* where it is currently mapped */
+	int fd; /* open file descriptor for the database */
+	tdb_len_t map_size; /* how much space has been mapped */
+	int read_only; /* opened read-only */
+	int traverse_read; /* read-only traversal */
+	struct tdb_lock_type global_lock;
+	int num_lockrecs;
+	struct tdb_lock_type *lockrecs; /* only real locks, all with count>0 */
+	enum TDB_ERROR ecode; /* error code for last tdb error */
+	struct tdb_header header; /* a cached copy of the header */
+	u32 flags; /* the flags passed to tdb_open */
+	struct tdb_traverse_lock travlocks; /* current traversal locks */
+	struct tdb_context *next; /* all tdbs to avoid multiple opens */
+	dev_t device;	/* uniquely identifies this tdb */
+	ino_t inode;	/* uniquely identifies this tdb */
+	struct tdb_logging_context log;
+	unsigned int (*hash_fn)(TDB_DATA *key);
+	int open_flags; /* flags used in the open - needed by reopen */
+	unsigned int num_locks; /* number of chain locks held */
+	const struct tdb_methods *methods;
+	struct tdb_transaction *transaction;
+	int page_size;
+	int max_dead_records;
+	bool have_transaction_lock;
+	tdb_len_t real_map_size; /* how much space has been mapped */
+};
+
+
+/*
+  internal prototypes
+*/
+static int tdb_munmap(struct tdb_context *tdb);
+static void tdb_mmap(struct tdb_context *tdb);
+static int tdb_lock(struct tdb_context *tdb, int list, int ltype);
+int tdb_lock_nonblock(struct tdb_context *tdb, int list, int ltype);
+static int tdb_unlock(struct tdb_context *tdb, int list, int ltype);
+static int tdb_brlock(struct tdb_context *tdb, tdb_off_t offset, int rw_type, int lck_type, int probe, size_t len);
+static int tdb_transaction_lock(struct tdb_context *tdb, int ltype);
+static int tdb_transaction_unlock(struct tdb_context *tdb);
+static int tdb_brlock_upgrade(struct tdb_context *tdb, tdb_off_t offset, size_t len);
+static int tdb_write_lock_record(struct tdb_context *tdb, tdb_off_t off);
+static int tdb_write_unlock_record(struct tdb_context *tdb, tdb_off_t off);
+static int tdb_ofs_read(struct tdb_context *tdb, tdb_off_t offset, tdb_off_t *d);
+static int tdb_ofs_write(struct tdb_context *tdb, tdb_off_t offset, tdb_off_t *d);
+static void *tdb_convert(void *buf, u32 size);
+static int tdb_free(struct tdb_context *tdb, tdb_off_t offset, struct list_struct *rec);
+static tdb_off_t tdb_allocate(struct tdb_context *tdb, tdb_len_t length, struct list_struct *rec);
+static int tdb_ofs_read(struct tdb_context *tdb, tdb_off_t offset, tdb_off_t *d);
+static int tdb_ofs_write(struct tdb_context *tdb, tdb_off_t offset, tdb_off_t *d);
+static int tdb_lock_record(struct tdb_context *tdb, tdb_off_t off);
+static int tdb_unlock_record(struct tdb_context *tdb, tdb_off_t off);
+static int tdb_rec_read(struct tdb_context *tdb, tdb_off_t offset, struct list_struct *rec);
+static int tdb_rec_write(struct tdb_context *tdb, tdb_off_t offset, struct list_struct *rec);
+static int tdb_do_delete(struct tdb_context *tdb, tdb_off_t rec_ptr, struct list_struct *rec);
+static unsigned char *tdb_alloc_read(struct tdb_context *tdb, tdb_off_t offset, tdb_len_t len);
+static int tdb_parse_data(struct tdb_context *tdb, TDB_DATA key,
+		   tdb_off_t offset, tdb_len_t len,
+		   int (*parser)(TDB_DATA key, TDB_DATA data,
+				 void *private_data),
+		   void *private_data);
+static tdb_off_t tdb_find_lock_hash(struct tdb_context *tdb, TDB_DATA key, u32 hash, int locktype,
+			   struct list_struct *rec);
+static void tdb_io_init(struct tdb_context *tdb);
+static int tdb_expand(struct tdb_context *tdb, tdb_off_t size);
+static int tdb_rec_free_read(struct tdb_context *tdb, tdb_off_t off,
+		      struct list_struct *rec);
+
+
+/* file: error.c */
+
+enum TDB_ERROR tdb_error(struct tdb_context *tdb)
+{
+	return tdb->ecode;
+}
+
+static struct tdb_errname {
+	enum TDB_ERROR ecode; const char *estring;
+} emap[] = { {TDB_SUCCESS, "Success"},
+	     {TDB_ERR_CORRUPT, "Corrupt database"},
+	     {TDB_ERR_IO, "IO Error"},
+	     {TDB_ERR_LOCK, "Locking error"},
+	     {TDB_ERR_OOM, "Out of memory"},
+	     {TDB_ERR_EXISTS, "Record exists"},
+	     {TDB_ERR_NOLOCK, "Lock exists on other keys"},
+	     {TDB_ERR_EINVAL, "Invalid parameter"},
+	     {TDB_ERR_NOEXIST, "Record does not exist"},
+	     {TDB_ERR_RDONLY, "write not permitted"} };
+
+/* Error string for the last tdb error */
+const char *tdb_errorstr(struct tdb_context *tdb)
+{
+	u32 i;
+	for (i = 0; i < sizeof(emap) / sizeof(struct tdb_errname); i++)
+		if (tdb->ecode == emap[i].ecode)
+			return emap[i].estring;
+	return "Invalid error code";
+}
+
+/* file: lock.c */
+
+#define TDB_MARK_LOCK 0x80000000
+
+/* a byte range locking function - return 0 on success
+   this functions locks/unlocks 1 byte at the specified offset.
+
+   On error, errno is also set so that errors are passed back properly
+   through tdb_open().
+
+   note that a len of zero means lock to end of file
+*/
+int tdb_brlock(struct tdb_context *tdb, tdb_off_t offset,
+	       int rw_type, int lck_type, int probe, size_t len)
+{
+	struct flock fl;
+	int ret;
+
+	if (tdb->flags & TDB_NOLOCK) {
+		return 0;
+	}
+
+	if ((rw_type == F_WRLCK) && (tdb->read_only || tdb->traverse_read)) {
+		tdb->ecode = TDB_ERR_RDONLY;
+		return -1;
+	}
+
+	fl.l_type = rw_type;
+	fl.l_whence = SEEK_SET;
+	fl.l_start = offset;
+	fl.l_len = len;
+	fl.l_pid = 0;
+
+	do {
+		ret = fcntl(tdb->fd,lck_type,&fl);
+	} while (ret == -1 && errno == EINTR);
+
+	if (ret == -1) {
+		/* Generic lock error. errno set by fcntl.
+		 * EAGAIN is an expected return from non-blocking
+		 * locks. */
+		if (!probe && lck_type != F_SETLK) {
+			/* Ensure error code is set for log fun to examine. */
+			tdb->ecode = TDB_ERR_LOCK;
+			TDB_LOG((tdb, TDB_DEBUG_TRACE,"tdb_brlock failed (fd=%d) at offset %d rw_type=%d lck_type=%d len=%d\n",
+				 tdb->fd, offset, rw_type, lck_type, (int)len));
+		}
+		return TDB_ERRCODE(TDB_ERR_LOCK, -1);
+	}
+	return 0;
+}
+
+
+/*
+  upgrade a read lock to a write lock. This needs to be handled in a
+  special way as some OSes (such as solaris) have too conservative
+  deadlock detection and claim a deadlock when progress can be
+  made. For those OSes we may loop for a while.
+*/
+int tdb_brlock_upgrade(struct tdb_context *tdb, tdb_off_t offset, size_t len)
+{
+	int count = 1000;
+	while (count--) {
+		struct timeval tv;
+		if (tdb_brlock(tdb, offset, F_WRLCK, F_SETLKW, 1, len) == 0) {
+			return 0;
+		}
+		if (errno != EDEADLK) {
+			break;
+		}
+		/* sleep for as short a time as we can - more portable than usleep() */
+		tv.tv_sec = 0;
+		tv.tv_usec = 1;
+		select(0, NULL, NULL, NULL, &tv);
+	}
+	TDB_LOG((tdb, TDB_DEBUG_TRACE,"tdb_brlock_upgrade failed at offset %d\n", offset));
+	return -1;
+}
+
+
+/* lock a list in the database. list -1 is the alloc list */
+static int _tdb_lock(struct tdb_context *tdb, int list, int ltype, int op)
+{
+	struct tdb_lock_type *new_lck;
+	int i;
+	bool mark_lock = ((ltype & TDB_MARK_LOCK) == TDB_MARK_LOCK);
+
+	ltype &= ~TDB_MARK_LOCK;
+
+	/* a global lock allows us to avoid per chain locks */
+	if (tdb->global_lock.count &&
+	    ((u32)ltype == tdb->global_lock.ltype || ltype == F_RDLCK)) {
+		return 0;
+	}
+
+	if (tdb->global_lock.count) {
+		return TDB_ERRCODE(TDB_ERR_LOCK, -1);
+	}
+
+	if (list < -1 || list >= (int)tdb->header.hash_size) {
+		TDB_LOG((tdb, TDB_DEBUG_ERROR,"tdb_lock: invalid list %d for ltype=%d\n",
+			   list, ltype));
+		return -1;
+	}
+	if (tdb->flags & TDB_NOLOCK)
+		return 0;
+
+	for (i=0; i<tdb->num_lockrecs; i++) {
+		if (tdb->lockrecs[i].list == list) {
+			if (tdb->lockrecs[i].count == 0) {
+				/*
+				 * Can't happen, see tdb_unlock(). It should
+				 * be an assert.
+				 */
+				TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lock: "
+					 "lck->count == 0 for list %d", list));
+			}
+			/*
+			 * Just increment the in-memory struct, posix locks
+			 * don't stack.
+			 */
+			tdb->lockrecs[i].count++;
+			return 0;
+		}
+	}
+
+	new_lck = (struct tdb_lock_type *)realloc(
+		tdb->lockrecs,
+		sizeof(*tdb->lockrecs) * (tdb->num_lockrecs+1));
+	if (new_lck == NULL) {
+		errno = ENOMEM;
+		return -1;
+	}
+	tdb->lockrecs = new_lck;
+
+	/* Since fcntl locks don't nest, we do a lock for the first one,
+	   and simply bump the count for future ones */
+	if (!mark_lock &&
+	    tdb->methods->tdb_brlock(tdb,FREELIST_TOP+4*list, ltype, op,
+				     0, 1)) {
+		return -1;
+	}
+
+	tdb->num_locks++;
+
+	tdb->lockrecs[tdb->num_lockrecs].list = list;
+	tdb->lockrecs[tdb->num_lockrecs].count = 1;
+	tdb->lockrecs[tdb->num_lockrecs].ltype = ltype;
+	tdb->num_lockrecs += 1;
+
+	return 0;
+}
+
+/* lock a list in the database. list -1 is the alloc list */
+int tdb_lock(struct tdb_context *tdb, int list, int ltype)
+{
+	int ret;
+	ret = _tdb_lock(tdb, list, ltype, F_SETLKW);
+	if (ret) {
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lock failed on list %d "
+			 "ltype=%d (%s)\n",  list, ltype, strerror(errno)));
+	}
+	return ret;
+}
+
+/* lock a list in the database. list -1 is the alloc list. non-blocking lock */
+int tdb_lock_nonblock(struct tdb_context *tdb, int list, int ltype)
+{
+	return _tdb_lock(tdb, list, ltype, F_SETLK);
+}
+
+
+/* unlock the database: returns void because it's too late for errors. */
+	/* changed to return int it may be interesting to know there
+	   has been an error  --simo */
+int tdb_unlock(struct tdb_context *tdb, int list, int ltype)
+{
+	int ret = -1;
+	int i;
+	struct tdb_lock_type *lck = NULL;
+	bool mark_lock = ((ltype & TDB_MARK_LOCK) == TDB_MARK_LOCK);
+
+	ltype &= ~TDB_MARK_LOCK;
+
+	/* a global lock allows us to avoid per chain locks */
+	if (tdb->global_lock.count &&
+	    ((u32)ltype == tdb->global_lock.ltype || ltype == F_RDLCK)) {
+		return 0;
+	}
+
+	if (tdb->global_lock.count) {
+		return TDB_ERRCODE(TDB_ERR_LOCK, -1);
+	}
+
+	if (tdb->flags & TDB_NOLOCK)
+		return 0;
+
+	/* Sanity checks */
+	if (list < -1 || list >= (int)tdb->header.hash_size) {
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: list %d invalid (%d)\n", list, tdb->header.hash_size));
+		return ret;
+	}
+
+	for (i=0; i<tdb->num_lockrecs; i++) {
+		if (tdb->lockrecs[i].list == list) {
+			lck = &tdb->lockrecs[i];
+			break;
+		}
+	}
+
+	if ((lck == NULL) || (lck->count == 0)) {
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: count is 0\n"));
+		return -1;
+	}
+
+	if (lck->count > 1) {
+		lck->count--;
+		return 0;
+	}
+
+	/*
+	 * This lock has count==1 left, so we need to unlock it in the
+	 * kernel. We don't bother with decrementing the in-memory array
+	 * element, we're about to overwrite it with the last array element
+	 * anyway.
+	 */
+
+	if (mark_lock) {
+		ret = 0;
+	} else {
+		ret = tdb->methods->tdb_brlock(tdb, FREELIST_TOP+4*list, F_UNLCK,
+					       F_SETLKW, 0, 1);
+	}
+	tdb->num_locks--;
+
+	/*
+	 * Shrink the array by overwriting the element just unlocked with the
+	 * last array element.
+	 */
+
+	if (tdb->num_lockrecs > 1) {
+		*lck = tdb->lockrecs[tdb->num_lockrecs-1];
+	}
+	tdb->num_lockrecs -= 1;
+
+	/*
+	 * We don't bother with realloc when the array shrinks, but if we have
+	 * a completely idle tdb we should get rid of the locked array.
+	 */
+
+	if (tdb->num_lockrecs == 0) {
+		SAFE_FREE(tdb->lockrecs);
+	}
+
+	if (ret)
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: An error occurred unlocking!\n"));
+	return ret;
+}
+
+/*
+  get the transaction lock
+ */
+int tdb_transaction_lock(struct tdb_context *tdb, int ltype)
+{
+	if (tdb->have_transaction_lock || tdb->global_lock.count) {
+		return 0;
+	}
+	if (tdb->methods->tdb_brlock(tdb, TRANSACTION_LOCK, ltype,
+				     F_SETLKW, 0, 1) == -1) {
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_lock: failed to get transaction lock\n"));
+		tdb->ecode = TDB_ERR_LOCK;
+		return -1;
+	}
+	tdb->have_transaction_lock = 1;
+	return 0;
+}
+
+/*
+  release the transaction lock
+ */
+int tdb_transaction_unlock(struct tdb_context *tdb)
+{
+	int ret;
+	if (!tdb->have_transaction_lock) {
+		return 0;
+	}
+	ret = tdb->methods->tdb_brlock(tdb, TRANSACTION_LOCK, F_UNLCK, F_SETLKW, 0, 1);
+	if (ret == 0) {
+		tdb->have_transaction_lock = 0;
+	}
+	return ret;
+}
+
+
+
+
+/* lock/unlock entire database */
+static int _tdb_lockall(struct tdb_context *tdb, int ltype, int op)
+{
+	bool mark_lock = ((ltype & TDB_MARK_LOCK) == TDB_MARK_LOCK);
+
+	ltype &= ~TDB_MARK_LOCK;
+
+	/* There are no locks on read-only dbs */
+	if (tdb->read_only || tdb->traverse_read)
+		return TDB_ERRCODE(TDB_ERR_LOCK, -1);
+
+	if (tdb->global_lock.count && tdb->global_lock.ltype == (u32)ltype) {
+		tdb->global_lock.count++;
+		return 0;
+	}
+
+	if (tdb->global_lock.count) {
+		/* a global lock of a different type exists */
+		return TDB_ERRCODE(TDB_ERR_LOCK, -1);
+	}
+
+	if (tdb->num_locks != 0) {
+		/* can't combine global and chain locks */
+		return TDB_ERRCODE(TDB_ERR_LOCK, -1);
+	}
+
+	if (!mark_lock &&
+	    tdb->methods->tdb_brlock(tdb, FREELIST_TOP, ltype, op,
+				     0, 4*tdb->header.hash_size)) {
+		if (op == F_SETLKW) {
+			TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lockall failed (%s)\n", strerror(errno)));
+		}
+		return -1;
+	}
+
+	tdb->global_lock.count = 1;
+	tdb->global_lock.ltype = ltype;
+
+	return 0;
+}
+
+
+
+/* unlock entire db */
+static int _tdb_unlockall(struct tdb_context *tdb, int ltype)
+{
+	bool mark_lock = ((ltype & TDB_MARK_LOCK) == TDB_MARK_LOCK);
+
+	ltype &= ~TDB_MARK_LOCK;
+
+	/* There are no locks on read-only dbs */
+	if (tdb->read_only || tdb->traverse_read) {
+		return TDB_ERRCODE(TDB_ERR_LOCK, -1);
+	}
+
+	if (tdb->global_lock.ltype != (u32)ltype ||
+	    tdb->global_lock.count == 0) {
+		return TDB_ERRCODE(TDB_ERR_LOCK, -1);
+	}
+
+	if (tdb->global_lock.count > 1) {
+		tdb->global_lock.count--;
+		return 0;
+	}
+
+	if (!mark_lock &&
+	    tdb->methods->tdb_brlock(tdb, FREELIST_TOP, F_UNLCK, F_SETLKW,
+				     0, 4*tdb->header.hash_size)) {
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlockall failed (%s)\n", strerror(errno)));
+		return -1;
+	}
+
+	tdb->global_lock.count = 0;
+	tdb->global_lock.ltype = 0;
+
+	return 0;
+}
+
+/* lock entire database with write lock */
+int tdb_lockall(struct tdb_context *tdb)
+{
+	return _tdb_lockall(tdb, F_WRLCK, F_SETLKW);
+}
+
+/* lock entire database with write lock - mark only */
+int tdb_lockall_mark(struct tdb_context *tdb)
+{
+	return _tdb_lockall(tdb, F_WRLCK | TDB_MARK_LOCK, F_SETLKW);
+}
+
+/* unlock entire database with write lock - unmark only */
+int tdb_lockall_unmark(struct tdb_context *tdb)
+{
+	return _tdb_unlockall(tdb, F_WRLCK | TDB_MARK_LOCK);
+}
+
+/* lock entire database with write lock - nonblocking variant */
+int tdb_lockall_nonblock(struct tdb_context *tdb)
+{
+	return _tdb_lockall(tdb, F_WRLCK, F_SETLK);
+}
+
+/* unlock entire database with write lock */
+int tdb_unlockall(struct tdb_context *tdb)
+{
+	return _tdb_unlockall(tdb, F_WRLCK);
+}
+
+/* lock entire database with read lock */
+int tdb_lockall_read(struct tdb_context *tdb)
+{
+	return _tdb_lockall(tdb, F_RDLCK, F_SETLKW);
+}
+
+/* lock entire database with read lock - nonblock variant */
+int tdb_lockall_read_nonblock(struct tdb_context *tdb)
+{
+	return _tdb_lockall(tdb, F_RDLCK, F_SETLK);
+}
+
+/* unlock entire database with read lock */
+int tdb_unlockall_read(struct tdb_context *tdb)
+{
+	return _tdb_unlockall(tdb, F_RDLCK);
+}
+
+/* lock/unlock one hash chain. This is meant to be used to reduce
+   contention - it cannot guarantee how many records will be locked */
+int tdb_chainlock(struct tdb_context *tdb, TDB_DATA key)
+{
+	return tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
+}
+
+/* lock/unlock one hash chain, non-blocking. This is meant to be used
+   to reduce contention - it cannot guarantee how many records will be
+   locked */
+int tdb_chainlock_nonblock(struct tdb_context *tdb, TDB_DATA key)
+{
+	return tdb_lock_nonblock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
+}
+
+/* mark a chain as locked without actually locking it. Warning! use with great caution! */
+int tdb_chainlock_mark(struct tdb_context *tdb, TDB_DATA key)
+{
+	return tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK | TDB_MARK_LOCK);
+}
+
+/* unmark a chain as locked without actually locking it. Warning! use with great caution! */
+int tdb_chainlock_unmark(struct tdb_context *tdb, TDB_DATA key)
+{
+	return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK | TDB_MARK_LOCK);
+}
+
+int tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key)
+{
+	return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
+}
+
+int tdb_chainlock_read(struct tdb_context *tdb, TDB_DATA key)
+{
+	return tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_RDLCK);
+}
+
+int tdb_chainunlock_read(struct tdb_context *tdb, TDB_DATA key)
+{
+	return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_RDLCK);
+}
+
+
+
+/* record lock stops delete underneath */
+int tdb_lock_record(struct tdb_context *tdb, tdb_off_t off)
+{
+	return off ? tdb->methods->tdb_brlock(tdb, off, F_RDLCK, F_SETLKW, 0, 1) : 0;
+}
+
+/*
+  Write locks override our own fcntl readlocks, so check it here.
+  Note this is meant to be F_SETLK, *not* F_SETLKW, as it's not
+  an error to fail to get the lock here.
+*/
+int tdb_write_lock_record(struct tdb_context *tdb, tdb_off_t off)
+{
+	struct tdb_traverse_lock *i;
+	for (i = &tdb->travlocks; i; i = i->next)
+		if (i->off == off)
+			return -1;
+	return tdb->methods->tdb_brlock(tdb, off, F_WRLCK, F_SETLK, 1, 1);
+}
+
+/*
+  Note this is meant to be F_SETLK, *not* F_SETLKW, as it's not
+  an error to fail to get the lock here.
+*/
+int tdb_write_unlock_record(struct tdb_context *tdb, tdb_off_t off)
+{
+	return tdb->methods->tdb_brlock(tdb, off, F_UNLCK, F_SETLK, 0, 1);
+}
+
+/* fcntl locks don't stack: avoid unlocking someone else's */
+int tdb_unlock_record(struct tdb_context *tdb, tdb_off_t off)
+{
+	struct tdb_traverse_lock *i;
+	u32 count = 0;
+
+	if (off == 0)
+		return 0;
+	for (i = &tdb->travlocks; i; i = i->next)
+		if (i->off == off)
+			count++;
+	return (count == 1 ? tdb->methods->tdb_brlock(tdb, off, F_UNLCK, F_SETLKW, 0, 1) : 0);
+}
+
+/* file: io.c */
+
+/* check for an out of bounds access - if it is out of bounds then
+   see if the database has been expanded by someone else and expand
+   if necessary
+   note that "len" is the minimum length needed for the db
+*/
+static int tdb_oob(struct tdb_context *tdb, tdb_off_t len, int probe)
+{
+	struct stat st;
+	if (len <= tdb->map_size)
+		return 0;
+	if (tdb->flags & TDB_INTERNAL) {
+		if (!probe) {
+			/* Ensure ecode is set for log fn. */
+			tdb->ecode = TDB_ERR_IO;
+			TDB_LOG((tdb, TDB_DEBUG_FATAL,"tdb_oob len %d beyond internal malloc size %d\n",
+				 (int)len, (int)tdb->map_size));
+		}
+		return TDB_ERRCODE(TDB_ERR_IO, -1);
+	}
+
+	if (fstat(tdb->fd, &st) == -1) {
+		return TDB_ERRCODE(TDB_ERR_IO, -1);
+	}
+
+	if (st.st_size < (off_t)len) {
+		if (!probe) {
+			/* Ensure ecode is set for log fn. */
+			tdb->ecode = TDB_ERR_IO;
+			TDB_LOG((tdb, TDB_DEBUG_FATAL,"tdb_oob len %d beyond eof at %d\n",
+				 (int)len, (int)st.st_size));
+		}
+		return TDB_ERRCODE(TDB_ERR_IO, -1);
+	}
+
+	/* Unmap, update size, remap */
+	if (tdb_munmap(tdb) == -1)
+		return TDB_ERRCODE(TDB_ERR_IO, -1);
+	tdb->map_size = st.st_size;
+	tdb_mmap(tdb);
+	return 0;
+}
+
+/* write a lump of data at a specified offset */
+static int tdb_write(struct tdb_context *tdb, tdb_off_t off,
+		     const void *buf, tdb_len_t len)
+{
+	if (len == 0) {
+		return 0;
+	}
+
+	if (tdb->read_only || tdb->traverse_read) {
+		tdb->ecode = TDB_ERR_RDONLY;
+		return -1;
+	}
+
+	if (tdb->methods->tdb_oob(tdb, off + len, 0) != 0)
+		return -1;
+
+	if (tdb->map_ptr) {
+		memcpy(off + (char *)tdb->map_ptr, buf, len);
+	} else if (pwrite(tdb->fd, buf, len, off) != (ssize_t)len) {
+		/* Ensure ecode is set for log fn. */
+		tdb->ecode = TDB_ERR_IO;
+		TDB_LOG((tdb, TDB_DEBUG_FATAL,"tdb_write failed at %d len=%d (%s)\n",
+			   off, len, strerror(errno)));
+		return TDB_ERRCODE(TDB_ERR_IO, -1);
+	}
+	return 0;
+}
+
+/* Endian conversion: we only ever deal with 4 byte quantities */
+void *tdb_convert(void *buf, u32 size)
+{
+	u32 i, *p = (u32 *)buf;
+	for (i = 0; i < size / 4; i++)
+		p[i] = TDB_BYTEREV(p[i]);
+	return buf;
+}
+
+
+/* read a lump of data at a specified offset, maybe convert */
+static int tdb_read(struct tdb_context *tdb, tdb_off_t off, void *buf,
+		    tdb_len_t len, int cv)
+{
+	if (tdb->methods->tdb_oob(tdb, off + len, 0) != 0) {
+		return -1;
+	}
+
+	if (tdb->map_ptr) {
+		memcpy(buf, off + (char *)tdb->map_ptr, len);
+	} else {
+		ssize_t ret = pread(tdb->fd, buf, len, off);
+		if (ret != (ssize_t)len) {
+			/* Ensure ecode is set for log fn. */
+			tdb->ecode = TDB_ERR_IO;
+			TDB_LOG((tdb, TDB_DEBUG_FATAL,"tdb_read failed at %d "
+				 "len=%d ret=%d (%s) map_size=%d\n",
+				 (int)off, (int)len, (int)ret, strerror(errno),
+				 (int)tdb->map_size));
+			return TDB_ERRCODE(TDB_ERR_IO, -1);
+		}
+	}
+	if (cv) {
+		tdb_convert(buf, len);
+	}
+	return 0;
+}
+
+
+
+/*
+  do an unlocked scan of the hash table heads to find the next non-zero head. The value
+  will then be confirmed with the lock held
+*/
+static void tdb_next_hash_chain(struct tdb_context *tdb, u32 *chain)
+{
+	u32 h = *chain;
+	if (tdb->map_ptr) {
+		for (;h < tdb->header.hash_size;h++) {
+			if (0 != *(u32 *)(TDB_HASH_TOP(h) + (unsigned char *)tdb->map_ptr)) {
+				break;
+			}
+		}
+	} else {
+		u32 off=0;
+		for (;h < tdb->header.hash_size;h++) {
+			if (tdb_ofs_read(tdb, TDB_HASH_TOP(h), &off) != 0 || off != 0) {
+				break;
+			}
+		}
+	}
+	(*chain) = h;
+}
+
+
+int tdb_munmap(struct tdb_context *tdb)
+{
+	if (tdb->flags & TDB_INTERNAL)
+		return 0;
+
+#ifdef HAVE_MMAP
+	if (tdb->map_ptr) {
+		int ret = munmap(tdb->map_ptr, tdb->real_map_size);
+		if (ret != 0)
+			return ret;
+		tdb->real_map_size = 0;
+	}
+#endif
+	tdb->map_ptr = NULL;
+	return 0;
+}
+
+void tdb_mmap(struct tdb_context *tdb)
+{
+	if (tdb->flags & TDB_INTERNAL)
+		return;
+
+#ifdef HAVE_MMAP
+	if (!(tdb->flags & TDB_NOMMAP)) {
+		tdb->map_ptr = mmap(NULL, tdb->map_size,
+				    PROT_READ|(tdb->read_only? 0:PROT_WRITE),
+				    MAP_SHARED|MAP_FILE, tdb->fd, 0);
+
+		/*
+		 * NB. When mmap fails it returns MAP_FAILED *NOT* NULL !!!!
+		 */
+
+		if (tdb->map_ptr == MAP_FAILED) {
+			tdb->real_map_size = 0;
+			tdb->map_ptr = NULL;
+			TDB_LOG((tdb, TDB_DEBUG_WARNING, "tdb_mmap failed for size %d (%s)\n",
+				 tdb->map_size, strerror(errno)));
+		}
+		tdb->real_map_size = tdb->map_size;
+	} else {
+		tdb->map_ptr = NULL;
+	}
+#else
+	tdb->map_ptr = NULL;
+#endif
+}
+
+/* expand a file.  we prefer to use ftruncate, as that is what posix
+  says to use for mmap expansion */
+static int tdb_expand_file(struct tdb_context *tdb, tdb_off_t size, tdb_off_t addition)
+{
+	char buf[1024];
+
+	if (tdb->read_only || tdb->traverse_read) {
+		tdb->ecode = TDB_ERR_RDONLY;
+		return -1;
+	}
+
+	if (ftruncate(tdb->fd, size+addition) == -1) {
+		char b = 0;
+		if (pwrite(tdb->fd,  &b, 1, (size+addition) - 1) != 1) {
+			TDB_LOG((tdb, TDB_DEBUG_FATAL, "expand_file to %d failed (%s)\n",
+				 size+addition, strerror(errno)));
+			return -1;
+		}
+	}
+
+	/* now fill the file with something. This ensures that the
+	   file isn't sparse, which would be very bad if we ran out of
+	   disk. This must be done with write, not via mmap */
+	memset(buf, TDB_PAD_BYTE, sizeof(buf));
+	while (addition) {
+		int n = addition>sizeof(buf)?sizeof(buf):addition;
+		int ret = pwrite(tdb->fd, buf, n, size);
+		if (ret != n) {
+			TDB_LOG((tdb, TDB_DEBUG_FATAL, "expand_file write of %d failed (%s)\n",
+				   n, strerror(errno)));
+			return -1;
+		}
+		addition -= n;
+		size += n;
+	}
+	return 0;
+}
+
+
+/* expand the database at least size bytes by expanding the underlying
+   file and doing the mmap again if necessary */
+int tdb_expand(struct tdb_context *tdb, tdb_off_t size)
+{
+	struct list_struct rec;
+	tdb_off_t offset;
+
+	if (tdb_lock(tdb, -1, F_WRLCK) == -1) {
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "lock failed in tdb_expand\n"));
+		return -1;
+	}
+
+	/* must know about any previous expansions by another process */
+	tdb->methods->tdb_oob(tdb, tdb->map_size + 1, 1);
+
+	/* always make room for at least 10 more records, and round
+           the database up to a multiple of the page size */
+	size = TDB_ALIGN(tdb->map_size + size*10, tdb->page_size) - tdb->map_size;
+
+	if (!(tdb->flags & TDB_INTERNAL))
+		tdb_munmap(tdb);
+
+	/*
+	 * We must ensure the file is unmapped before doing this
+	 * to ensure consistency with systems like OpenBSD where
+	 * writes and mmaps are not consistent.
+	 */
+
+	/* expand the file itself */
+	if (!(tdb->flags & TDB_INTERNAL)) {
+		if (tdb->methods->tdb_expand_file(tdb, tdb->map_size, size) != 0)
+			goto fail;
+	}
+
+	tdb->map_size += size;
+
+	if (tdb->flags & TDB_INTERNAL) {
+		char *new_map_ptr = (char *)realloc(tdb->map_ptr,
+						    tdb->map_size);
+		if (!new_map_ptr) {
+			tdb->map_size -= size;
+			goto fail;
+		}
+		tdb->map_ptr = new_map_ptr;
+	} else {
+		/*
+		 * We must ensure the file is remapped before adding the space
+		 * to ensure consistency with systems like OpenBSD where
+		 * writes and mmaps are not consistent.
+		 */
+
+		/* We're ok if the mmap fails as we'll fallback to read/write */
+		tdb_mmap(tdb);
+	}
+
+	/* form a new freelist record */
+	memset(&rec,'\0',sizeof(rec));
+	rec.rec_len = size - sizeof(rec);
+
+	/* link it into the free list */
+	offset = tdb->map_size - size;
+	if (tdb_free(tdb, offset, &rec) == -1)
+		goto fail;
+
+	tdb_unlock(tdb, -1, F_WRLCK);
+	return 0;
+ fail:
+	tdb_unlock(tdb, -1, F_WRLCK);
+	return -1;
+}
+
+/* read/write a tdb_off_t */
+int tdb_ofs_read(struct tdb_context *tdb, tdb_off_t offset, tdb_off_t *d)
+{
+	return tdb->methods->tdb_read(tdb, offset, (char*)d, sizeof(*d), DOCONV());
+}
+
+int tdb_ofs_write(struct tdb_context *tdb, tdb_off_t offset, tdb_off_t *d)
+{
+	tdb_off_t off = *d;
+	return tdb->methods->tdb_write(tdb, offset, CONVERT(off), sizeof(*d));
+}
+
+
+/* read a lump of data, allocating the space for it */
+unsigned char *tdb_alloc_read(struct tdb_context *tdb, tdb_off_t offset, tdb_len_t len)
+{
+	unsigned char *buf;
+
+	/* some systems don't like zero length malloc */
+	if (len == 0) {
+		len = 1;
+	}
+
+	if (!(buf = (unsigned char *)malloc(len))) {
+		/* Ensure ecode is set for log fn. */
+		tdb->ecode = TDB_ERR_OOM;
+		TDB_LOG((tdb, TDB_DEBUG_ERROR,"tdb_alloc_read malloc failed len=%d (%s)\n",
+			   len, strerror(errno)));
+		return TDB_ERRCODE(TDB_ERR_OOM, buf);
+	}
+	if (tdb->methods->tdb_read(tdb, offset, buf, len, 0) == -1) {
+		SAFE_FREE(buf);
+		return NULL;
+	}
+	return buf;
+}
+
+/* Give a piece of tdb data to a parser */
+
+int tdb_parse_data(struct tdb_context *tdb, TDB_DATA key,
+		   tdb_off_t offset, tdb_len_t len,
+		   int (*parser)(TDB_DATA key, TDB_DATA data,
+				 void *private_data),
+		   void *private_data)
+{
+	TDB_DATA data;
+	int result;
+
+	data.dsize = len;
+
+	if ((tdb->transaction == NULL) && (tdb->map_ptr != NULL)) {
+		/*
+		 * Optimize by avoiding the malloc/memcpy/free, point the
+		 * parser directly at the mmap area.
+		 */
+		if (tdb->methods->tdb_oob(tdb, offset+len, 0) != 0) {
+			return -1;
+		}
+		data.dptr = offset + (unsigned char *)tdb->map_ptr;
+		return parser(key, data, private_data);
+	}
+
+	if (!(data.dptr = tdb_alloc_read(tdb, offset, len))) {
+		return -1;
+	}
+
+	result = parser(key, data, private_data);
+	free(data.dptr);
+	return result;
+}
+
+/* read/write a record */
+int tdb_rec_read(struct tdb_context *tdb, tdb_off_t offset, struct list_struct *rec)
+{
+	if (tdb->methods->tdb_read(tdb, offset, rec, sizeof(*rec),DOCONV()) == -1)
+		return -1;
+	if (TDB_BAD_MAGIC(rec)) {
+		/* Ensure ecode is set for log fn. */
+		tdb->ecode = TDB_ERR_CORRUPT;
+		TDB_LOG((tdb, TDB_DEBUG_FATAL,"tdb_rec_read bad magic 0x%x at offset=%d\n", rec->magic, offset));
+		return TDB_ERRCODE(TDB_ERR_CORRUPT, -1);
+	}
+	return tdb->methods->tdb_oob(tdb, rec->next+sizeof(*rec), 0);
+}
+
+int tdb_rec_write(struct tdb_context *tdb, tdb_off_t offset, struct list_struct *rec)
+{
+	struct list_struct r = *rec;
+	return tdb->methods->tdb_write(tdb, offset, CONVERT(r), sizeof(r));
+}
+
+static const struct tdb_methods io_methods = {
+	tdb_read,
+	tdb_write,
+	tdb_next_hash_chain,
+	tdb_oob,
+	tdb_expand_file,
+	tdb_brlock
+};
+
+/*
+  initialise the default methods table
+*/
+void tdb_io_init(struct tdb_context *tdb)
+{
+	tdb->methods = &io_methods;
+}
+
+/* file: transaction.c */
+
+/*
+  transaction design:
+
+  - only allow a single transaction at a time per database. This makes
+    using the transaction API simpler, as otherwise the caller would
+    have to cope with temporary failures in transactions that conflict
+    with other current transactions
+
+  - keep the transaction recovery information in the same file as the
+    database, using a special 'transaction recovery' record pointed at
+    by the header. This removes the need for extra journal files as
+    used by some other databases
+
+  - dynamically allocated the transaction recover record, re-using it
+    for subsequent transactions. If a larger record is needed then
+    tdb_free() the old record to place it on the normal tdb freelist
+    before allocating the new record
+
+  - during transactions, keep a linked list of writes all that have
+    been performed by intercepting all tdb_write() calls. The hooked
+    transaction versions of tdb_read() and tdb_write() check this
+    linked list and try to use the elements of the list in preference
+    to the real database.
+
+  - don't allow any locks to be held when a transaction starts,
+    otherwise we can end up with deadlock (plus lack of lock nesting
+    in posix locks would mean the lock is lost)
+
+  - if the caller gains a lock during the transaction but doesn't
+    release it then fail the commit
+
+  - allow for nested calls to tdb_transaction_start(), re-using the
+    existing transaction record. If the inner transaction is cancelled
+    then a subsequent commit will fail
+
+  - keep a mirrored copy of the tdb hash chain heads to allow for the
+    fast hash heads scan on traverse, updating the mirrored copy in
+    the transaction version of tdb_write
+
+  - allow callers to mix transaction and non-transaction use of tdb,
+    although once a transaction is started then an exclusive lock is
+    gained until the transaction is committed or cancelled
+
+  - the commit strategy involves first saving away all modified data
+    into a linearised buffer in the transaction recovery area, then
+    marking the transaction recovery area with a magic value to
+    indicate a valid recovery record. In total 4 fsync/msync calls are
+    needed per commit to prevent race conditions. It might be possible
+    to reduce this to 3 or even 2 with some more work.
+
+  - check for a valid recovery record on open of the tdb, while the
+    global lock is held. Automatically recover from the transaction
+    recovery area if needed, then continue with the open as
+    usual. This allows for smooth crash recovery with no administrator
+    intervention.
+
+  - if TDB_NOSYNC is passed to flags in tdb_open then transactions are
+    still available, but no transaction recovery area is used and no
+    fsync/msync calls are made.
+
+*/
+
+struct tdb_transaction_el {
+	struct tdb_transaction_el *next, *prev;
+	tdb_off_t offset;
+	tdb_len_t length;
+	unsigned char *data;
+};
+
+/*
+  hold the context of any current transaction
+*/
+struct tdb_transaction {
+	/* we keep a mirrored copy of the tdb hash heads here so
+	   tdb_next_hash_chain() can operate efficiently */
+	u32 *hash_heads;
+
+	/* the original io methods - used to do IOs to the real db */
+	const struct tdb_methods *io_methods;
+
+	/* the list of transaction elements. We use a doubly linked
+	   list with a last pointer to allow us to keep the list
+	   ordered, with first element at the front of the list. It
+	   needs to be doubly linked as the read/write traversals need
+	   to be backwards, while the commit needs to be forwards */
+	struct tdb_transaction_el *elements, *elements_last;
+
+	/* non-zero when an internal transaction error has
+	   occurred. All write operations will then fail until the
+	   transaction is ended */
+	int transaction_error;
+
+	/* when inside a transaction we need to keep track of any
+	   nested tdb_transaction_start() calls, as these are allowed,
+	   but don't create a new transaction */
+	int nesting;
+
+	/* old file size before transaction */
+	tdb_len_t old_map_size;
+};
+
+
+/*
+  read while in a transaction. We need to check first if the data is in our list
+  of transaction elements, then if not do a real read
+*/
+static int transaction_read(struct tdb_context *tdb, tdb_off_t off, void *buf,
+			    tdb_len_t len, int cv)
+{
+	struct tdb_transaction_el *el;
+
+	/* we need to walk the list backwards to get the most recent data */
+	for (el=tdb->transaction->elements_last;el;el=el->prev) {
+		tdb_len_t partial;
+
+		if (off+len <= el->offset) {
+			continue;
+		}
+		if (off >= el->offset + el->length) {
+			continue;
+		}
+
+		/* an overlapping read - needs to be split into up to
+		   2 reads and a memcpy */
+		if (off < el->offset) {
+			partial = el->offset - off;
+			if (transaction_read(tdb, off, buf, partial, cv) != 0) {
+				goto fail;
+			}
+			len -= partial;
+			off += partial;
+			buf = (void *)(partial + (char *)buf);
+		}
+		if (off + len <= el->offset + el->length) {
+			partial = len;
+		} else {
+			partial = el->offset + el->length - off;
+		}
+		memcpy(buf, el->data + (off - el->offset), partial);
+		if (cv) {
+			tdb_convert(buf, len);
+		}
+		len -= partial;
+		off += partial;
+		buf = (void *)(partial + (char *)buf);
+
+		if (len != 0 && transaction_read(tdb, off, buf, len, cv) != 0) {
+			goto fail;
+		}
+
+		return 0;
+	}
+
+	/* its not in the transaction elements - do a real read */
+	return tdb->transaction->io_methods->tdb_read(tdb, off, buf, len, cv);
+
+fail:
+	TDB_LOG((tdb, TDB_DEBUG_FATAL, "transaction_read: failed at off=%d len=%d\n", off, len));
+	tdb->ecode = TDB_ERR_IO;
+	tdb->transaction->transaction_error = 1;
+	return -1;
+}
+
+
+/*
+  write while in a transaction
+*/
+static int transaction_write(struct tdb_context *tdb, tdb_off_t off,
+			     const void *buf, tdb_len_t len)
+{
+	struct tdb_transaction_el *el, *best_el=NULL;
+
+	if (len == 0) {
+		return 0;
+	}
+
+	/* if the write is to a hash head, then update the transaction
+	   hash heads */
+	if (len == sizeof(tdb_off_t) && off >= FREELIST_TOP &&
+	    off < FREELIST_TOP+TDB_HASHTABLE_SIZE(tdb)) {
+		u32 chain = (off-FREELIST_TOP) / sizeof(tdb_off_t);
+		memcpy(&tdb->transaction->hash_heads[chain], buf, len);
+	}
+
+	/* first see if we can replace an existing entry */
+	for (el=tdb->transaction->elements_last;el;el=el->prev) {
+		tdb_len_t partial;
+
+		if (best_el == NULL && off == el->offset+el->length) {
+			best_el = el;
+		}
+
+		if (off+len <= el->offset) {
+			continue;
+		}
+		if (off >= el->offset + el->length) {
+			continue;
+		}
+
+		/* an overlapping write - needs to be split into up to
+		   2 writes and a memcpy */
+		if (off < el->offset) {
+			partial = el->offset - off;
+			if (transaction_write(tdb, off, buf, partial) != 0) {
+				goto fail;
+			}
+			len -= partial;
+			off += partial;
+			buf = (const void *)(partial + (const char *)buf);
+		}
+		if (off + len <= el->offset + el->length) {
+			partial = len;
+		} else {
+			partial = el->offset + el->length - off;
+		}
+		memcpy(el->data + (off - el->offset), buf, partial);
+		len -= partial;
+		off += partial;
+		buf = (const void *)(partial + (const char *)buf);
+
+		if (len != 0 && transaction_write(tdb, off, buf, len) != 0) {
+			goto fail;
+		}
+
+		return 0;
+	}
+
+	/* see if we can append the new entry to an existing entry */
+	if (best_el && best_el->offset + best_el->length == off &&
+	    (off+len < tdb->transaction->old_map_size ||
+	     off > tdb->transaction->old_map_size)) {
+		unsigned char *data = best_el->data;
+		el = best_el;
+		el->data = (unsigned char *)realloc(el->data,
+						    el->length + len);
+		if (el->data == NULL) {
+			tdb->ecode = TDB_ERR_OOM;
+			tdb->transaction->transaction_error = 1;
+			el->data = data;
+			return -1;
+		}
+		if (buf) {
+			memcpy(el->data + el->length, buf, len);
+		} else {
+			memset(el->data + el->length, TDB_PAD_BYTE, len);
+		}
+		el->length += len;
+		return 0;
+	}
+
+	/* add a new entry at the end of the list */
+	el = (struct tdb_transaction_el *)malloc(sizeof(*el));
+	if (el == NULL) {
+		tdb->ecode = TDB_ERR_OOM;
+		tdb->transaction->transaction_error = 1;
+		return -1;
+	}
+	el->next = NULL;
+	el->prev = tdb->transaction->elements_last;
+	el->offset = off;
+	el->length = len;
+	el->data = (unsigned char *)malloc(len);
+	if (el->data == NULL) {
+		free(el);
+		tdb->ecode = TDB_ERR_OOM;
+		tdb->transaction->transaction_error = 1;
+		return -1;
+	}
+	if (buf) {
+		memcpy(el->data, buf, len);
+	} else {
+		memset(el->data, TDB_PAD_BYTE, len);
+	}
+	if (el->prev) {
+		el->prev->next = el;
+	} else {
+		tdb->transaction->elements = el;
+	}
+	tdb->transaction->elements_last = el;
+	return 0;
+
+fail:
+	TDB_LOG((tdb, TDB_DEBUG_FATAL, "transaction_write: failed at off=%d len=%d\n", off, len));
+	tdb->ecode = TDB_ERR_IO;
+	tdb->transaction->transaction_error = 1;
+	return -1;
+}
+
+/*
+  accelerated hash chain head search, using the cached hash heads
+*/
+static void transaction_next_hash_chain(struct tdb_context *tdb, u32 *chain)
+{
+	u32 h = *chain;
+	for (;h < tdb->header.hash_size;h++) {
+		/* the +1 takes account of the freelist */
+		if (0 != tdb->transaction->hash_heads[h+1]) {
+			break;
+		}
+	}
+	(*chain) = h;
+}
+
+/*
+  out of bounds check during a transaction
+*/
+static int transaction_oob(struct tdb_context *tdb, tdb_off_t len,
+			   int probe EXT2FS_ATTR((unused)))
+{
+	if (len <= tdb->map_size) {
+		return 0;
+	}
+	return TDB_ERRCODE(TDB_ERR_IO, -1);
+}
+
+/*
+  transaction version of tdb_expand().
+*/
+static int transaction_expand_file(struct tdb_context *tdb, tdb_off_t size,
+				   tdb_off_t addition)
+{
+	/* add a write to the transaction elements, so subsequent
+	   reads see the zero data */
+	if (transaction_write(tdb, size, NULL, addition) != 0) {
+		return -1;
+	}
+
+	return 0;
+}
+
+/*
+  brlock during a transaction - ignore them
+*/
+static int transaction_brlock(struct tdb_context *tdb EXT2FS_ATTR((unused)),
+			      tdb_off_t offset EXT2FS_ATTR((unused)),
+			      int rw_type EXT2FS_ATTR((unused)),
+			      int lck_type EXT2FS_ATTR((unused)),
+			      int probe EXT2FS_ATTR((unused)),
+			      size_t len EXT2FS_ATTR((unused)))
+{
+	return 0;
+}
+
+static const struct tdb_methods transaction_methods = {
+	transaction_read,
+	transaction_write,
+	transaction_next_hash_chain,
+	transaction_oob,
+	transaction_expand_file,
+	transaction_brlock
+};
+
+
+/*
+  start a tdb transaction. No token is returned, as only a single
+  transaction is allowed to be pending per tdb_context
+*/
+int tdb_transaction_start(struct tdb_context *tdb)
+{
+	/* some sanity checks */
+	if (tdb->read_only || (tdb->flags & TDB_INTERNAL) || tdb->traverse_read) {
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: cannot start a transaction on a read-only or internal db\n"));
+		tdb->ecode = TDB_ERR_EINVAL;
+		return -1;
+	}
+
+	/* cope with nested tdb_transaction_start() calls */
+	if (tdb->transaction != NULL) {
+		tdb->transaction->nesting++;
+		TDB_LOG((tdb, TDB_DEBUG_TRACE, "tdb_transaction_start: nesting %d\n",
+			 tdb->transaction->nesting));
+		return 0;
+	}
+
+	if (tdb->num_locks != 0 || tdb->global_lock.count) {
+		/* the caller must not have any locks when starting a
+		   transaction as otherwise we'll be screwed by lack
+		   of nested locks in posix */
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: cannot start a transaction with locks held\n"));
+		tdb->ecode = TDB_ERR_LOCK;
+		return -1;
+	}
+
+	if (tdb->travlocks.next != NULL) {
+		/* you cannot use transactions inside a traverse (although you can use
+		   traverse inside a transaction) as otherwise you can end up with
+		   deadlock */
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: cannot start a transaction within a traverse\n"));
+		tdb->ecode = TDB_ERR_LOCK;
+		return -1;
+	}
+
+	tdb->transaction = (struct tdb_transaction *)
+		calloc(sizeof(struct tdb_transaction), 1);
+	if (tdb->transaction == NULL) {
+		tdb->ecode = TDB_ERR_OOM;
+		return -1;
+	}
+
+	/* get the transaction write lock. This is a blocking lock. As
+	   discussed with Volker, there are a number of ways we could
+	   make this async, which we will probably do in the future */
+	if (tdb_transaction_lock(tdb, F_WRLCK) == -1) {
+		SAFE_FREE(tdb->transaction);
+		return -1;
+	}
+
+	/* get a read lock from the freelist to the end of file. This
+	   is upgraded to a write lock during the commit */
+	if (tdb_brlock(tdb, FREELIST_TOP, F_RDLCK, F_SETLKW, 0, 0) == -1) {
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: failed to get hash locks\n"));
+		tdb->ecode = TDB_ERR_LOCK;
+		goto fail;
+	}
+
+	/* setup a copy of the hash table heads so the hash scan in
+	   traverse can be fast */
+	tdb->transaction->hash_heads = (u32 *)
+		calloc(tdb->header.hash_size+1, sizeof(u32));
+	if (tdb->transaction->hash_heads == NULL) {
+		tdb->ecode = TDB_ERR_OOM;
+		goto fail;
+	}
+	if (tdb->methods->tdb_read(tdb, FREELIST_TOP, tdb->transaction->hash_heads,
+				   TDB_HASHTABLE_SIZE(tdb), 0) != 0) {
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_start: failed to read hash heads\n"));
+		tdb->ecode = TDB_ERR_IO;
+		goto fail;
+	}
+
+	/* make sure we know about any file expansions already done by
+	   anyone else */
+	tdb->methods->tdb_oob(tdb, tdb->map_size + 1, 1);
+	tdb->transaction->old_map_size = tdb->map_size;
+
+	/* finally hook the io methods, replacing them with
+	   transaction specific methods */
+	tdb->transaction->io_methods = tdb->methods;
+	tdb->methods = &transaction_methods;
+
+	/* by calling this transaction write here, we ensure that we don't grow the
+	   transaction linked list due to hash table updates */
+	if (transaction_write(tdb, FREELIST_TOP, tdb->transaction->hash_heads,
+			      TDB_HASHTABLE_SIZE(tdb)) != 0) {
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_start: failed to prime hash table\n"));
+		tdb->ecode = TDB_ERR_IO;
+		tdb->methods = tdb->transaction->io_methods;
+		goto fail;
+	}
+
+	return 0;
+
+fail:
+	tdb_brlock(tdb, FREELIST_TOP, F_UNLCK, F_SETLKW, 0, 0);
+	tdb_transaction_unlock(tdb);
+	SAFE_FREE(tdb->transaction->hash_heads);
+	SAFE_FREE(tdb->transaction);
+	return -1;
+}
+
+
+/*
+  cancel the current transaction
+*/
+int tdb_transaction_cancel(struct tdb_context *tdb)
+{
+	if (tdb->transaction == NULL) {
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_cancel: no transaction\n"));
+		return -1;
+	}
+
+	if (tdb->transaction->nesting != 0) {
+		tdb->transaction->transaction_error = 1;
+		tdb->transaction->nesting--;
+		return 0;
+	}
+
+	tdb->map_size = tdb->transaction->old_map_size;
+
+	/* free all the transaction elements */
+	while (tdb->transaction->elements) {
+		struct tdb_transaction_el *el = tdb->transaction->elements;
+		tdb->transaction->elements = el->next;
+		free(el->data);
+		free(el);
+	}
+
+	/* remove any global lock created during the transaction */
+	if (tdb->global_lock.count != 0) {
+		tdb_brlock(tdb, FREELIST_TOP, F_UNLCK, F_SETLKW, 0, 4*tdb->header.hash_size);
+		tdb->global_lock.count = 0;
+	}
+
+	/* remove any locks created during the transaction */
+	if (tdb->num_locks != 0) {
+		int i;
+		for (i=0;i<tdb->num_lockrecs;i++) {
+			tdb_brlock(tdb,FREELIST_TOP+4*tdb->lockrecs[i].list,
+				   F_UNLCK,F_SETLKW, 0, 1);
+		}
+		tdb->num_locks = 0;
+		tdb->num_lockrecs = 0;
+		SAFE_FREE(tdb->lockrecs);
+	}
+
+	/* restore the normal io methods */
+	tdb->methods = tdb->transaction->io_methods;
+
+	tdb_brlock(tdb, FREELIST_TOP, F_UNLCK, F_SETLKW, 0, 0);
+	tdb_transaction_unlock(tdb);
+	SAFE_FREE(tdb->transaction->hash_heads);
+	SAFE_FREE(tdb->transaction);
+
+	return 0;
+}
+
+/*
+  sync to disk
+*/
+static int transaction_sync(struct tdb_context *tdb, tdb_off_t offset, tdb_len_t length)
+{
+	if (fsync(tdb->fd) != 0) {
+		tdb->ecode = TDB_ERR_IO;
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction: fsync failed\n"));
+		return -1;
+	}
+#if defined(HAVE_MSYNC) && defined(MS_SYNC)
+	if (tdb->map_ptr) {
+		tdb_off_t moffset = offset & ~(tdb->page_size-1);
+		if (msync(moffset + (char *)tdb->map_ptr,
+			  length + (offset - moffset), MS_SYNC) != 0) {
+			tdb->ecode = TDB_ERR_IO;
+			TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction: msync failed - %s\n",
+				 strerror(errno)));
+			return -1;
+		}
+	}
+#endif
+	return 0;
+}
+
+
+/*
+  work out how much space the linearised recovery data will consume
+*/
+static tdb_len_t tdb_recovery_size(struct tdb_context *tdb)
+{
+	struct tdb_transaction_el *el;
+	tdb_len_t recovery_size = 0;
+
+	recovery_size = sizeof(u32);
+	for (el=tdb->transaction->elements;el;el=el->next) {
+		if (el->offset >= tdb->transaction->old_map_size) {
+			continue;
+		}
+		recovery_size += 2*sizeof(tdb_off_t) + el->length;
+	}
+
+	return recovery_size;
+}
+
+/*
+  allocate the recovery area, or use an existing recovery area if it is
+  large enough
+*/
+static int tdb_recovery_allocate(struct tdb_context *tdb,
+				 tdb_len_t *recovery_size,
+				 tdb_off_t *recovery_offset,
+				 tdb_len_t *recovery_max_size)
+{
+	struct list_struct rec;
+	const struct tdb_methods *methods = tdb->transaction->io_methods;
+	tdb_off_t recovery_head;
+
+	if (tdb_ofs_read(tdb, TDB_RECOVERY_HEAD, &recovery_head) == -1) {
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to read recovery head\n"));
+		return -1;
+	}
+
+	rec.rec_len = 0;
+
+	if (recovery_head != 0 &&
+	    methods->tdb_read(tdb, recovery_head, &rec, sizeof(rec), DOCONV()) == -1) {
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to read recovery record\n"));
+		return -1;
+	}
+
+	*recovery_size = tdb_recovery_size(tdb);
+
+	if (recovery_head != 0 && *recovery_size <= rec.rec_len) {
+		/* it fits in the existing area */
+		*recovery_max_size = rec.rec_len;
+		*recovery_offset = recovery_head;
+		return 0;
+	}
+
+	/* we need to free up the old recovery area, then allocate a
+	   new one at the end of the file. Note that we cannot use
+	   tdb_allocate() to allocate the new one as that might return
+	   us an area that is being currently used (as of the start of
+	   the transaction) */
+	if (recovery_head != 0) {
+		if (tdb_free(tdb, recovery_head, &rec) == -1) {
+			TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to free previous recovery area\n"));
+			return -1;
+		}
+	}
+
+	/* the tdb_free() call might have increased the recovery size */
+	*recovery_size = tdb_recovery_size(tdb);
+
+	/* round up to a multiple of page size */
+	*recovery_max_size = TDB_ALIGN(sizeof(rec) + *recovery_size, tdb->page_size) - sizeof(rec);
+	*recovery_offset = tdb->map_size;
+	recovery_head = *recovery_offset;
+
+	if (methods->tdb_expand_file(tdb, tdb->transaction->old_map_size,
+				     (tdb->map_size - tdb->transaction->old_map_size) +
+				     sizeof(rec) + *recovery_max_size) == -1) {
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to create recovery area\n"));
+		return -1;
+	}
+
+	/* remap the file (if using mmap) */
+	methods->tdb_oob(tdb, tdb->map_size + 1, 1);
+
+	/* we have to reset the old map size so that we don't try to expand the file
+	   again in the transaction commit, which would destroy the recovery area */
+	tdb->transaction->old_map_size = tdb->map_size;
+
+	/* write the recovery header offset and sync - we can sync without a race here
+	   as the magic ptr in the recovery record has not been set */
+	CONVERT(recovery_head);
+	if (methods->tdb_write(tdb, TDB_RECOVERY_HEAD,
+			       &recovery_head, sizeof(tdb_off_t)) == -1) {
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to write recovery head\n"));
+		return -1;
+	}
+
+	return 0;
+}
+
+
+/*
+  setup the recovery data that will be used on a crash during commit
+*/
+static int transaction_setup_recovery(struct tdb_context *tdb,
+				      tdb_off_t *magic_offset)
+{
+	struct tdb_transaction_el *el;
+	tdb_len_t recovery_size;
+	unsigned char *data, *p;
+	const struct tdb_methods *methods = tdb->transaction->io_methods;
+	struct list_struct *rec;
+	tdb_off_t recovery_offset, recovery_max_size;
+	tdb_off_t old_map_size = tdb->transaction->old_map_size;
+	u32 magic, tailer;
+
+	/*
+	  check that the recovery area has enough space
+	*/
+	if (tdb_recovery_allocate(tdb, &recovery_size,
+				  &recovery_offset, &recovery_max_size) == -1) {
+		return -1;
+	}
+
+	data = (unsigned char *)malloc(recovery_size + sizeof(*rec));
+	if (data == NULL) {
+		tdb->ecode = TDB_ERR_OOM;
+		return -1;
+	}
+
+	rec = (struct list_struct *)data;
+	memset(rec, 0, sizeof(*rec));
+
+	rec->magic    = 0;
+	rec->data_len = recovery_size;
+	rec->rec_len  = recovery_max_size;
+	rec->key_len  = old_map_size;
+	CONVERT(rec);
+
+	/* build the recovery data into a single blob to allow us to do a single
+	   large write, which should be more efficient */
+	p = data + sizeof(*rec);
+	for (el=tdb->transaction->elements;el;el=el->next) {
+		if (el->offset >= old_map_size) {
+			continue;
+		}
+		if (el->offset + el->length > tdb->transaction->old_map_size) {
+			TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: transaction data over new region boundary\n"));
+			free(data);
+			tdb->ecode = TDB_ERR_CORRUPT;
+			return -1;
+		}
+		memcpy(p, &el->offset, 4);
+		memcpy(p+4, &el->length, 4);
+		if (DOCONV()) {
+			tdb_convert(p, 8);
+		}
+		/* the recovery area contains the old data, not the
+		   new data, so we have to call the original tdb_read
+		   method to get it */
+		if (methods->tdb_read(tdb, el->offset, p + 8, el->length, 0) != 0) {
+			free(data);
+			tdb->ecode = TDB_ERR_IO;
+			return -1;
+		}
+		p += 8 + el->length;
+	}
+
+	/* and the tailer */
+	tailer = sizeof(*rec) + recovery_max_size;
+	memcpy(p, &tailer, 4);
+	CONVERT(p);
+
+	/* write the recovery data to the recovery area */
+	if (methods->tdb_write(tdb, recovery_offset, data, sizeof(*rec) + recovery_size) == -1) {
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write recovery data\n"));
+		free(data);
+		tdb->ecode = TDB_ERR_IO;
+		return -1;
+	}
+
+	/* as we don't have ordered writes, we have to sync the recovery
+	   data before we update the magic to indicate that the recovery
+	   data is present */
+	if (transaction_sync(tdb, recovery_offset, sizeof(*rec) + recovery_size) == -1) {
+		free(data);
+		return -1;
+	}
+
+	free(data);
+
+	magic = TDB_RECOVERY_MAGIC;
+	CONVERT(magic);
+
+	*magic_offset = recovery_offset + offsetof(struct list_struct, magic);
+
+	if (methods->tdb_write(tdb, *magic_offset, &magic, sizeof(magic)) == -1) {
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write recovery magic\n"));
+		tdb->ecode = TDB_ERR_IO;
+		return -1;
+	}
+
+	/* ensure the recovery magic marker is on disk */
+	if (transaction_sync(tdb, *magic_offset, sizeof(magic)) == -1) {
+		return -1;
+	}
+
+	return 0;
+}
+
+/*
+  commit the current transaction
+*/
+int tdb_transaction_commit(struct tdb_context *tdb)
+{
+	const struct tdb_methods *methods;
+	tdb_off_t magic_offset = 0;
+	u32 zero = 0;
+
+	if (tdb->transaction == NULL) {
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_commit: no transaction\n"));
+		return -1;
+	}
+
+	if (tdb->transaction->transaction_error) {
+		tdb->ecode = TDB_ERR_IO;
+		tdb_transaction_cancel(tdb);
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_commit: transaction error pending\n"));
+		return -1;
+	}
+
+	if (tdb->transaction->nesting != 0) {
+		tdb->transaction->nesting--;
+		return 0;
+	}
+
+	/* check for a null transaction */
+	if (tdb->transaction->elements == NULL) {
+		tdb_transaction_cancel(tdb);
+		return 0;
+	}
+
+	methods = tdb->transaction->io_methods;
+
+	/* if there are any locks pending then the caller has not
+	   nested their locks properly, so fail the transaction */
+	if (tdb->num_locks || tdb->global_lock.count) {
+		tdb->ecode = TDB_ERR_LOCK;
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_commit: locks pending on commit\n"));
+		tdb_transaction_cancel(tdb);
+		return -1;
+	}
+
+	/* upgrade the main transaction lock region to a write lock */
+	if (tdb_brlock_upgrade(tdb, FREELIST_TOP, 0) == -1) {
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: failed to upgrade hash locks\n"));
+		tdb->ecode = TDB_ERR_LOCK;
+		tdb_transaction_cancel(tdb);
+		return -1;
+	}
+
+	/* get the global lock - this prevents new users attaching to the database
+	   during the commit */
+	if (tdb_brlock(tdb, GLOBAL_LOCK, F_WRLCK, F_SETLKW, 0, 1) == -1) {
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_commit: failed to get global lock\n"));
+		tdb->ecode = TDB_ERR_LOCK;
+		tdb_transaction_cancel(tdb);
+		return -1;
+	}
+
+	if (!(tdb->flags & TDB_NOSYNC)) {
+		/* write the recovery data to the end of the file */
+		if (transaction_setup_recovery(tdb, &magic_offset) == -1) {
+			TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_commit: failed to setup recovery data\n"));
+			tdb_brlock(tdb, GLOBAL_LOCK, F_UNLCK, F_SETLKW, 0, 1);
+			tdb_transaction_cancel(tdb);
+			return -1;
+		}
+	}
+
+	/* expand the file to the new size if needed */
+	if (tdb->map_size != tdb->transaction->old_map_size) {
+		if (methods->tdb_expand_file(tdb, tdb->transaction->old_map_size,
+					     tdb->map_size -
+					     tdb->transaction->old_map_size) == -1) {
+			tdb->ecode = TDB_ERR_IO;
+			TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_commit: expansion failed\n"));
+			tdb_brlock(tdb, GLOBAL_LOCK, F_UNLCK, F_SETLKW, 0, 1);
+			tdb_transaction_cancel(tdb);
+			return -1;
+		}
+		tdb->map_size = tdb->transaction->old_map_size;
+		methods->tdb_oob(tdb, tdb->map_size + 1, 1);
+	}
+
+	/* perform all the writes */
+	while (tdb->transaction->elements) {
+		struct tdb_transaction_el *el = tdb->transaction->elements;
+
+		if (methods->tdb_write(tdb, el->offset, el->data, el->length) == -1) {
+			TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_commit: write failed during commit\n"));
+
+			/* we've overwritten part of the data and
+			   possibly expanded the file, so we need to
+			   run the crash recovery code */
+			tdb->methods = methods;
+			tdb_transaction_recover(tdb);
+
+			tdb_transaction_cancel(tdb);
+			tdb_brlock(tdb, GLOBAL_LOCK, F_UNLCK, F_SETLKW, 0, 1);
+
+			TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_commit: write failed\n"));
+			return -1;
+		}
+		tdb->transaction->elements = el->next;
+		free(el->data);
+		free(el);
+	}
+
+	if (!(tdb->flags & TDB_NOSYNC)) {
+		/* ensure the new data is on disk */
+		if (transaction_sync(tdb, 0, tdb->map_size) == -1) {
+			return -1;
+		}
+
+		/* remove the recovery marker */
+		if (methods->tdb_write(tdb, magic_offset, &zero, 4) == -1) {
+			TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_commit: failed to remove recovery magic\n"));
+			return -1;
+		}
+
+		/* ensure the recovery marker has been removed on disk */
+		if (transaction_sync(tdb, magic_offset, 4) == -1) {
+			return -1;
+		}
+	}
+
+	tdb_brlock(tdb, GLOBAL_LOCK, F_UNLCK, F_SETLKW, 0, 1);
+
+	/*
+	  TODO: maybe write to some dummy hdr field, or write to magic
+	  offset without mmap, before the last sync, instead of the
+	  utime() call
+	*/
+
+	/* on some systems (like Linux 2.6.x) changes via mmap/msync
+	   don't change the mtime of the file, this means the file may
+	   not be backed up (as tdb rounding to block sizes means that
+	   file size changes are quite rare too). The following forces
+	   mtime changes when a transaction completes */
+#ifdef HAVE_UTIME
+	utime(tdb->name, NULL);
+#endif
+
+	/* use a transaction cancel to free memory and remove the
+	   transaction locks */
+	tdb_transaction_cancel(tdb);
+	return 0;
+}
+
+
+/*
+  recover from an aborted transaction. Must be called with exclusive
+  database write access already established (including the global
+  lock to prevent new processes attaching)
+*/
+int tdb_transaction_recover(struct tdb_context *tdb)
+{
+	tdb_off_t recovery_head, recovery_eof;
+	unsigned char *data, *p;
+	u32 zero = 0;
+	struct list_struct rec;
+
+	/* find the recovery area */
+	if (tdb_ofs_read(tdb, TDB_RECOVERY_HEAD, &recovery_head) == -1) {
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to read recovery head\n"));
+		tdb->ecode = TDB_ERR_IO;
+		return -1;
+	}
+
+	if (recovery_head == 0) {
+		/* we have never allocated a recovery record */
+		return 0;
+	}
+
+	/* read the recovery record */
+	if (tdb->methods->tdb_read(tdb, recovery_head, &rec,
+				   sizeof(rec), DOCONV()) == -1) {
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to read recovery record\n"));
+		tdb->ecode = TDB_ERR_IO;
+		return -1;
+	}
+
+	if (rec.magic != TDB_RECOVERY_MAGIC) {
+		/* there is no valid recovery data */
+		return 0;
+	}
+
+	if (tdb->read_only) {
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: attempt to recover read only database\n"));
+		tdb->ecode = TDB_ERR_CORRUPT;
+		return -1;
+	}
+
+	recovery_eof = rec.key_len;
+
+	data = (unsigned char *)malloc(rec.data_len);
+	if (data == NULL) {
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to allocate recovery data\n"));
+		tdb->ecode = TDB_ERR_OOM;
+		return -1;
+	}
+
+	/* read the full recovery data */
+	if (tdb->methods->tdb_read(tdb, recovery_head + sizeof(rec), data,
+				   rec.data_len, 0) == -1) {
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to read recovery data\n"));
+		tdb->ecode = TDB_ERR_IO;
+		free(data);
+		return -1;
+	}
+
+	/* recover the file data */
+	p = data;
+	while (p+8 < data + rec.data_len) {
+		u32 ofs, len;
+		if (DOCONV()) {
+			tdb_convert(p, 8);
+		}
+		memcpy(&ofs, p, 4);
+		memcpy(&len, p+4, 4);
+
+		if (tdb->methods->tdb_write(tdb, ofs, p+8, len) == -1) {
+			free(data);
+			TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to recover %d bytes at offset %d\n", len, ofs));
+			tdb->ecode = TDB_ERR_IO;
+			return -1;
+		}
+		p += 8 + len;
+	}
+
+	free(data);
+
+	if (transaction_sync(tdb, 0, tdb->map_size) == -1) {
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to sync recovery\n"));
+		tdb->ecode = TDB_ERR_IO;
+		return -1;
+	}
+
+	/* if the recovery area is after the recovered eof then remove it */
+	if (recovery_eof <= recovery_head) {
+		if (tdb_ofs_write(tdb, TDB_RECOVERY_HEAD, &zero) == -1) {
+			TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to remove recovery head\n"));
+			tdb->ecode = TDB_ERR_IO;
+			return -1;
+		}
+	}
+
+	/* remove the recovery magic */
+	if (tdb_ofs_write(tdb, recovery_head + offsetof(struct list_struct, magic),
+			  &zero) == -1) {
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to remove recovery magic\n"));
+		tdb->ecode = TDB_ERR_IO;
+		return -1;
+	}
+
+	/* reduce the file size to the old size */
+	tdb_munmap(tdb);
+	if (ftruncate(tdb->fd, recovery_eof) != 0) {
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to reduce to recovery size\n"));
+		tdb->ecode = TDB_ERR_IO;
+		return -1;
+	}
+	tdb->map_size = recovery_eof;
+	tdb_mmap(tdb);
+
+	if (transaction_sync(tdb, 0, recovery_eof) == -1) {
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to sync2 recovery\n"));
+		tdb->ecode = TDB_ERR_IO;
+		return -1;
+	}
+
+	TDB_LOG((tdb, TDB_DEBUG_TRACE, "tdb_transaction_recover: recovered %d byte database\n",
+		 recovery_eof));
+
+	/* all done */
+	return 0;
+}
+
+/* file: freelist.c */
+
+/* read a freelist record and check for simple errors */
+static int tdb_rec_free_read(struct tdb_context *tdb, tdb_off_t off, struct list_struct *rec)
+{
+	if (tdb->methods->tdb_read(tdb, off, rec, sizeof(*rec),DOCONV()) == -1)
+		return -1;
+
+	if (rec->magic == TDB_MAGIC) {
+		/* this happens when a app is showdown while deleting a record - we should
+		   not completely fail when this happens */
+		TDB_LOG((tdb, TDB_DEBUG_WARNING, "tdb_rec_free_read non-free magic 0x%x at offset=%d - fixing\n",
+			 rec->magic, off));
+		rec->magic = TDB_FREE_MAGIC;
+		if (tdb->methods->tdb_write(tdb, off, rec, sizeof(*rec)) == -1)
+			return -1;
+	}
+
+	if (rec->magic != TDB_FREE_MAGIC) {
+		/* Ensure ecode is set for log fn. */
+		tdb->ecode = TDB_ERR_CORRUPT;
+		TDB_LOG((tdb, TDB_DEBUG_WARNING, "tdb_rec_free_read bad magic 0x%x at offset=%d\n",
+			   rec->magic, off));
+		return TDB_ERRCODE(TDB_ERR_CORRUPT, -1);
+	}
+	if (tdb->methods->tdb_oob(tdb, rec->next+sizeof(*rec), 0) != 0)
+		return -1;
+	return 0;
+}
+
+
+
+/* Remove an element from the freelist.  Must have alloc lock. */
+static int remove_from_freelist(struct tdb_context *tdb, tdb_off_t off, tdb_off_t next)
+{
+	tdb_off_t last_ptr, i;
+
+	/* read in the freelist top */
+	last_ptr = FREELIST_TOP;
+	while (tdb_ofs_read(tdb, last_ptr, &i) != -1 && i != 0) {
+		if (i == off) {
+			/* We've found it! */
+			return tdb_ofs_write(tdb, last_ptr, &next);
+		}
+		/* Follow chain (next offset is at start of record) */
+		last_ptr = i;
+	}
+	TDB_LOG((tdb, TDB_DEBUG_FATAL,"remove_from_freelist: not on list at off=%d\n", off));
+	return TDB_ERRCODE(TDB_ERR_CORRUPT, -1);
+}
+
+
+/* update a record tailer (must hold allocation lock) */
+static int update_tailer(struct tdb_context *tdb, tdb_off_t offset,
+			 const struct list_struct *rec)
+{
+	tdb_off_t totalsize;
+
+	/* Offset of tailer from record header */
+	totalsize = sizeof(*rec) + rec->rec_len;
+	return tdb_ofs_write(tdb, offset + totalsize - sizeof(tdb_off_t),
+			 &totalsize);
+}
+
+/* Add an element into the freelist. Merge adjacent records if
+   necessary. */
+int tdb_free(struct tdb_context *tdb, tdb_off_t offset, struct list_struct *rec)
+{
+	tdb_off_t right, left;
+
+	/* Allocation and tailer lock */
+	if (tdb_lock(tdb, -1, F_WRLCK) != 0)
+		return -1;
+
+	/* set an initial tailer, so if we fail we don't leave a bogus record */
+	if (update_tailer(tdb, offset, rec) != 0) {
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_free: update_tailer failed!\n"));
+		goto fail;
+	}
+
+	/* Look right first (I'm an Australian, dammit) */
+	right = offset + sizeof(*rec) + rec->rec_len;
+	if (right + sizeof(*rec) <= tdb->map_size) {
+		struct list_struct r;
+
+		if (tdb->methods->tdb_read(tdb, right, &r, sizeof(r), DOCONV()) == -1) {
+			TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_free: right read failed at %u\n", right));
+			goto left;
+		}
+
+		/* If it's free, expand to include it. */
+		if (r.magic == TDB_FREE_MAGIC) {
+			if (remove_from_freelist(tdb, right, r.next) == -1) {
+				TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_free: right free failed at %u\n", right));
+				goto left;
+			}
+			rec->rec_len += sizeof(r) + r.rec_len;
+		}
+	}
+
+left:
+	/* Look left */
+	left = offset - sizeof(tdb_off_t);
+	if (left > TDB_DATA_START(tdb->header.hash_size)) {
+		struct list_struct l;
+		tdb_off_t leftsize;
+
+		/* Read in tailer and jump back to header */
+		if (tdb_ofs_read(tdb, left, &leftsize) == -1) {
+			TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_free: left offset read failed at %u\n", left));
+			goto update;
+		}
+
+		/* it could be uninitialised data */
+		if (leftsize == 0 || leftsize == TDB_PAD_U32) {
+			goto update;
+		}
+
+		left = offset - leftsize;
+
+		/* Now read in record */
+		if (tdb->methods->tdb_read(tdb, left, &l, sizeof(l), DOCONV()) == -1) {
+			TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_free: left read failed at %u (%u)\n", left, leftsize));
+			goto update;
+		}
+
+		/* If it's free, expand to include it. */
+		if (l.magic == TDB_FREE_MAGIC) {
+			if (remove_from_freelist(tdb, left, l.next) == -1) {
+				TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_free: left free failed at %u\n", left));
+				goto update;
+			} else {
+				offset = left;
+				rec->rec_len += leftsize;
+			}
+		}
+	}
+
+update:
+	if (update_tailer(tdb, offset, rec) == -1) {
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_free: update_tailer failed at %u\n", offset));
+		goto fail;
+	}
+
+	/* Now, prepend to free list */
+	rec->magic = TDB_FREE_MAGIC;
+
+	if (tdb_ofs_read(tdb, FREELIST_TOP, &rec->next) == -1 ||
+	    tdb_rec_write(tdb, offset, rec) == -1 ||
+	    tdb_ofs_write(tdb, FREELIST_TOP, &offset) == -1) {
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_free record write failed at offset=%d\n", offset));
+		goto fail;
+	}
+
+	/* And we're done. */
+	tdb_unlock(tdb, -1, F_WRLCK);
+	return 0;
+
+ fail:
+	tdb_unlock(tdb, -1, F_WRLCK);
+	return -1;
+}
+
+
+/*
+   the core of tdb_allocate - called when we have decided which
+   free list entry to use
+ */
+static tdb_off_t tdb_allocate_ofs(struct tdb_context *tdb, tdb_len_t length, tdb_off_t rec_ptr,
+				struct list_struct *rec, tdb_off_t last_ptr)
+{
+	struct list_struct newrec;
+	tdb_off_t newrec_ptr;
+
+	memset(&newrec, '\0', sizeof(newrec));
+
+	/* found it - now possibly split it up  */
+	if (rec->rec_len > length + MIN_REC_SIZE) {
+		/* Length of left piece */
+		length = TDB_ALIGN(length, TDB_ALIGNMENT);
+
+		/* Right piece to go on free list */
+		newrec.rec_len = rec->rec_len - (sizeof(*rec) + length);
+		newrec_ptr = rec_ptr + sizeof(*rec) + length;
+
+		/* And left record is shortened */
+		rec->rec_len = length;
+	} else {
+		newrec_ptr = 0;
+	}
+
+	/* Remove allocated record from the free list */
+	if (tdb_ofs_write(tdb, last_ptr, &rec->next) == -1) {
+		return 0;
+	}
+
+	/* Update header: do this before we drop alloc
+	   lock, otherwise tdb_free() might try to
+	   merge with us, thinking we're free.
+	   (Thanks Jeremy Allison). */
+	rec->magic = TDB_MAGIC;
+	if (tdb_rec_write(tdb, rec_ptr, rec) == -1) {
+		return 0;
+	}
+
+	/* Did we create new block? */
+	if (newrec_ptr) {
+		/* Update allocated record tailer (we
+		   shortened it). */
+		if (update_tailer(tdb, rec_ptr, rec) == -1) {
+			return 0;
+		}
+
+		/* Free new record */
+		if (tdb_free(tdb, newrec_ptr, &newrec) == -1) {
+			return 0;
+		}
+	}
+
+	/* all done - return the new record offset */
+	return rec_ptr;
+}
+
+/* allocate some space from the free list. The offset returned points
+   to a unconnected list_struct within the database with room for at
+   least length bytes of total data
+
+   0 is returned if the space could not be allocated
+ */
+tdb_off_t tdb_allocate(struct tdb_context *tdb, tdb_len_t length, struct list_struct *rec)
+{
+	tdb_off_t rec_ptr, last_ptr, newrec_ptr;
+	struct {
+		tdb_off_t rec_ptr, last_ptr;
+		tdb_len_t rec_len;
+	} bestfit;
+
+	if (tdb_lock(tdb, -1, F_WRLCK) == -1)
+		return 0;
+
+	/* Extra bytes required for tailer */
+	length += sizeof(tdb_off_t);
+
+ again:
+	last_ptr = FREELIST_TOP;
+
+	/* read in the freelist top */
+	if (tdb_ofs_read(tdb, FREELIST_TOP, &rec_ptr) == -1)
+		goto fail;
+
+	bestfit.rec_ptr = 0;
+	bestfit.last_ptr = 0;
+	bestfit.rec_len = 0;
+
+	/*
+	   this is a best fit allocation strategy. Originally we used
+	   a first fit strategy, but it suffered from massive fragmentation
+	   issues when faced with a slowly increasing record size.
+	 */
+	while (rec_ptr) {
+		if (tdb_rec_free_read(tdb, rec_ptr, rec) == -1) {
+			goto fail;
+		}
+
+		if (rec->rec_len >= length) {
+			if (bestfit.rec_ptr == 0 ||
+			    rec->rec_len < bestfit.rec_len) {
+				bestfit.rec_len = rec->rec_len;
+				bestfit.rec_ptr = rec_ptr;
+				bestfit.last_ptr = last_ptr;
+				/* consider a fit to be good enough if
+				   we aren't wasting more than half
+				   the space */
+				if (bestfit.rec_len < 2*length) {
+					break;
+				}
+			}
+		}
+
+		/* move to the next record */
+		last_ptr = rec_ptr;
+		rec_ptr = rec->next;
+	}
+
+	if (bestfit.rec_ptr != 0) {
+		if (tdb_rec_free_read(tdb, bestfit.rec_ptr, rec) == -1) {
+			goto fail;
+		}
+
+		newrec_ptr = tdb_allocate_ofs(tdb, length, bestfit.rec_ptr, rec, bestfit.last_ptr);
+		tdb_unlock(tdb, -1, F_WRLCK);
+		return newrec_ptr;
+	}
+
+	/* we didn't find enough space. See if we can expand the
+	   database and if we can then try again */
+	if (tdb_expand(tdb, length + sizeof(*rec)) == 0)
+		goto again;
+ fail:
+	tdb_unlock(tdb, -1, F_WRLCK);
+	return 0;
+}
+
+/* file: freelistcheck.c */
+
+/* Check the freelist is good and contains no loops.
+   Very memory intensive - only do this as a consistency
+   checker. Heh heh - uses an in memory tdb as the storage
+   for the "seen" record list. For some reason this strikes
+   me as extremely clever as I don't have to write another tree
+   data structure implementation :-).
+ */
+
+static int seen_insert(struct tdb_context *mem_tdb, tdb_off_t rec_ptr)
+{
+	TDB_DATA key, data;
+
+	memset(&data, '\0', sizeof(data));
+	key.dptr = (unsigned char *)&rec_ptr;
+	key.dsize = sizeof(rec_ptr);
+	return tdb_store(mem_tdb, key, data, TDB_INSERT);
+}
+
+int tdb_validate_freelist(struct tdb_context *tdb, int *pnum_entries)
+{
+	struct tdb_context *mem_tdb = NULL;
+	struct list_struct rec;
+	tdb_off_t rec_ptr, last_ptr;
+	int ret = -1;
+
+	*pnum_entries = 0;
+
+	mem_tdb = tdb_open("flval", tdb->header.hash_size,
+				TDB_INTERNAL, O_RDWR, 0600);
+	if (!mem_tdb) {
+		return -1;
+	}
+
+	if (tdb_lock(tdb, -1, F_WRLCK) == -1) {
+		tdb_close(mem_tdb);
+		return 0;
+	}
+
+	last_ptr = FREELIST_TOP;
+
+	/* Store the FREELIST_TOP record. */
+	if (seen_insert(mem_tdb, last_ptr) == -1) {
+		ret = TDB_ERRCODE(TDB_ERR_CORRUPT, -1);
+		goto fail;
+	}
+
+	/* read in the freelist top */
+	if (tdb_ofs_read(tdb, FREELIST_TOP, &rec_ptr) == -1) {
+		goto fail;
+	}
+
+	while (rec_ptr) {
+
+		/* If we can't store this record (we've seen it
+		   before) then the free list has a loop and must
+		   be corrupt. */
+
+		if (seen_insert(mem_tdb, rec_ptr)) {
+			ret = TDB_ERRCODE(TDB_ERR_CORRUPT, -1);
+			goto fail;
+		}
+
+		if (tdb_rec_free_read(tdb, rec_ptr, &rec) == -1) {
+			goto fail;
+		}
+
+		/* move to the next record */
+		last_ptr = rec_ptr;
+		rec_ptr = rec.next;
+		*pnum_entries += 1;
+	}
+
+	ret = 0;
+
+  fail:
+
+	tdb_close(mem_tdb);
+	tdb_unlock(tdb, -1, F_WRLCK);
+	return ret;
+}
+
+/* file: traverse.c */
+
+/* Uses traverse lock: 0 = finish, -1 = error, other = record offset */
+static int tdb_next_lock(struct tdb_context *tdb, struct tdb_traverse_lock *tlock,
+			 struct list_struct *rec)
+{
+	int want_next = (tlock->off != 0);
+
+	/* Lock each chain from the start one. */
+	for (; tlock->hash < tdb->header.hash_size; tlock->hash++) {
+		if (!tlock->off && tlock->hash != 0) {
+			/* this is an optimisation for the common case where
+			   the hash chain is empty, which is particularly
+			   common for the use of tdb with ldb, where large
+			   hashes are used. In that case we spend most of our
+			   time in tdb_brlock(), locking empty hash chains.
+
+			   To avoid this, we do an unlocked pre-check to see
+			   if the hash chain is empty before starting to look
+			   inside it. If it is empty then we can avoid that
+			   hash chain. If it isn't empty then we can't believe
+			   the value we get back, as we read it without a
+			   lock, so instead we get the lock and re-fetch the
+			   value below.
+
+			   Notice that not doing this optimisation on the
+			   first hash chain is critical. We must guarantee
+			   that we have done at least one fcntl lock at the
+			   start of a search to guarantee that memory is
+			   coherent on SMP systems. If records are added by
+			   others during the search then that's OK, and we
+			   could possibly miss those with this trick, but we
+			   could miss them anyway without this trick, so the
+			   semantics don't change.
+
+			   With a non-indexed ldb search this trick gains us a
+			   factor of around 80 in speed on a linux 2.6.x
+			   system (testing using ldbtest).
+			*/
+			tdb->methods->next_hash_chain(tdb, &tlock->hash);
+			if (tlock->hash == tdb->header.hash_size) {
+				continue;
+			}
+		}
+
+		if (tdb_lock(tdb, tlock->hash, tlock->lock_rw) == -1)
+			return -1;
+
+		/* No previous record?  Start at top of chain. */
+		if (!tlock->off) {
+			if (tdb_ofs_read(tdb, TDB_HASH_TOP(tlock->hash),
+				     &tlock->off) == -1)
+				goto fail;
+		} else {
+			/* Otherwise unlock the previous record. */
+			if (tdb_unlock_record(tdb, tlock->off) != 0)
+				goto fail;
+		}
+
+		if (want_next) {
+			/* We have offset of old record: grab next */
+			if (tdb_rec_read(tdb, tlock->off, rec) == -1)
+				goto fail;
+			tlock->off = rec->next;
+		}
+
+		/* Iterate through chain */
+		while( tlock->off) {
+			tdb_off_t current;
+			if (tdb_rec_read(tdb, tlock->off, rec) == -1)
+				goto fail;
+
+			/* Detect infinite loops. From "Shlomi Yaakobovich" <Shlomi@exanet.com>. */
+			if (tlock->off == rec->next) {
+				TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_next_lock: loop detected.\n"));
+				goto fail;
+			}
+
+			if (!TDB_DEAD(rec)) {
+				/* Woohoo: we found one! */
+				if (tdb_lock_record(tdb, tlock->off) != 0)
+					goto fail;
+				return tlock->off;
+			}
+
+			/* Try to clean dead ones from old traverses */
+			current = tlock->off;
+			tlock->off = rec->next;
+			if (!(tdb->read_only || tdb->traverse_read) &&
+			    tdb_do_delete(tdb, current, rec) != 0)
+				goto fail;
+		}
+		tdb_unlock(tdb, tlock->hash, tlock->lock_rw);
+		want_next = 0;
+	}
+	/* We finished iteration without finding anything */
+	return TDB_ERRCODE(TDB_SUCCESS, 0);
+
+ fail:
+	tlock->off = 0;
+	if (tdb_unlock(tdb, tlock->hash, tlock->lock_rw) != 0)
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_next_lock: On error unlock failed!\n"));
+	return -1;
+}
+
+/* traverse the entire database - calling fn(tdb, key, data) on each element.
+   return -1 on error or the record count traversed
+   if fn is NULL then it is not called
+   a non-zero return value from fn() indicates that the traversal should stop
+  */
+static int tdb_traverse_internal(struct tdb_context *tdb,
+				 tdb_traverse_func fn, void *private_data,
+				 struct tdb_traverse_lock *tl)
+{
+	TDB_DATA key, dbuf;
+	struct list_struct rec;
+	int ret, count = 0;
+
+	/* This was in the initialization, above, but the IRIX compiler
+	 * did not like it.  crh
+	 */
+	tl->next = tdb->travlocks.next;
+
+	/* fcntl locks don't stack: beware traverse inside traverse */
+	tdb->travlocks.next = tl;
+
+	/* tdb_next_lock places locks on the record returned, and its chain */
+	while ((ret = tdb_next_lock(tdb, tl, &rec)) > 0) {
+		count++;
+		/* now read the full record */
+		key.dptr = tdb_alloc_read(tdb, tl->off + sizeof(rec),
+					  rec.key_len + rec.data_len);
+		if (!key.dptr) {
+			ret = -1;
+			if (tdb_unlock(tdb, tl->hash, tl->lock_rw) != 0)
+				goto out;
+			if (tdb_unlock_record(tdb, tl->off) != 0)
+				TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_traverse: key.dptr == NULL and unlock_record failed!\n"));
+			goto out;
+		}
+		key.dsize = rec.key_len;
+		dbuf.dptr = key.dptr + rec.key_len;
+		dbuf.dsize = rec.data_len;
+
+		/* Drop chain lock, call out */
+		if (tdb_unlock(tdb, tl->hash, tl->lock_rw) != 0) {
+			ret = -1;
+			SAFE_FREE(key.dptr);
+			goto out;
+		}
+		if (fn && fn(tdb, key, dbuf, private_data)) {
+			/* They want us to terminate traversal */
+			ret = count;
+			if (tdb_unlock_record(tdb, tl->off) != 0) {
+				TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_traverse: unlock_record failed!\n"));;
+				ret = -1;
+			}
+			SAFE_FREE(key.dptr);
+			goto out;
+		}
+		SAFE_FREE(key.dptr);
+	}
+out:
+	tdb->travlocks.next = tl->next;
+	if (ret < 0)
+		return -1;
+	else
+		return count;
+}
+
+
+/*
+  a write style traverse - temporarily marks the db read only
+*/
+int tdb_traverse_read(struct tdb_context *tdb,
+		      tdb_traverse_func fn, void *private_data)
+{
+	struct tdb_traverse_lock tl = { NULL, 0, 0, F_RDLCK };
+	int ret;
+
+	/* we need to get a read lock on the transaction lock here to
+	   cope with the lock ordering semantics of solaris10 */
+	if (tdb_transaction_lock(tdb, F_RDLCK)) {
+		return -1;
+	}
+
+	tdb->traverse_read++;
+	ret = tdb_traverse_internal(tdb, fn, private_data, &tl);
+	tdb->traverse_read--;
+
+	tdb_transaction_unlock(tdb);
+
+	return ret;
+}
+
+/*
+  a write style traverse - needs to get the transaction lock to
+  prevent deadlocks
+*/
+int tdb_traverse(struct tdb_context *tdb,
+		 tdb_traverse_func fn, void *private_data)
+{
+	struct tdb_traverse_lock tl = { NULL, 0, 0, F_WRLCK };
+	int ret;
+
+	if (tdb->read_only || tdb->traverse_read) {
+		return tdb_traverse_read(tdb, fn, private_data);
+	}
+
+	if (tdb_transaction_lock(tdb, F_WRLCK)) {
+		return -1;
+	}
+
+	ret = tdb_traverse_internal(tdb, fn, private_data, &tl);
+
+	tdb_transaction_unlock(tdb);
+
+	return ret;
+}
+
+
+/* find the first entry in the database and return its key */
+TDB_DATA tdb_firstkey(struct tdb_context *tdb)
+{
+	TDB_DATA key;
+	struct list_struct rec;
+
+	/* release any old lock */
+	if (tdb_unlock_record(tdb, tdb->travlocks.off) != 0)
+		return tdb_null;
+	tdb->travlocks.off = tdb->travlocks.hash = 0;
+	tdb->travlocks.lock_rw = F_RDLCK;
+
+	/* Grab first record: locks chain and returned record. */
+	if (tdb_next_lock(tdb, &tdb->travlocks, &rec) <= 0)
+		return tdb_null;
+	/* now read the key */
+	key.dsize = rec.key_len;
+	key.dptr =tdb_alloc_read(tdb,tdb->travlocks.off+sizeof(rec),key.dsize);
+
+	/* Unlock the hash chain of the record we just read. */
+	if (tdb_unlock(tdb, tdb->travlocks.hash, tdb->travlocks.lock_rw) != 0)
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_firstkey: error occurred while tdb_unlocking!\n"));
+	return key;
+}
+
+/* find the next entry in the database, returning its key */
+TDB_DATA tdb_nextkey(struct tdb_context *tdb, TDB_DATA oldkey)
+{
+	u32 oldhash;
+	TDB_DATA key = tdb_null;
+	struct list_struct rec;
+	unsigned char *k = NULL;
+
+	/* Is locked key the old key?  If so, traverse will be reliable. */
+	if (tdb->travlocks.off) {
+		if (tdb_lock(tdb,tdb->travlocks.hash,tdb->travlocks.lock_rw))
+			return tdb_null;
+		if (tdb_rec_read(tdb, tdb->travlocks.off, &rec) == -1
+		    || !(k = tdb_alloc_read(tdb,tdb->travlocks.off+sizeof(rec),
+					    rec.key_len))
+		    || memcmp(k, oldkey.dptr, oldkey.dsize) != 0) {
+			/* No, it wasn't: unlock it and start from scratch */
+			if (tdb_unlock_record(tdb, tdb->travlocks.off) != 0) {
+				SAFE_FREE(k);
+				return tdb_null;
+			}
+			if (tdb_unlock(tdb, tdb->travlocks.hash, tdb->travlocks.lock_rw) != 0) {
+				SAFE_FREE(k);
+				return tdb_null;
+			}
+			tdb->travlocks.off = 0;
+		}
+
+		SAFE_FREE(k);
+	}
+
+	if (!tdb->travlocks.off) {
+		/* No previous element: do normal find, and lock record */
+		tdb->travlocks.off = tdb_find_lock_hash(tdb, oldkey, tdb->hash_fn(&oldkey), tdb->travlocks.lock_rw, &rec);
+		if (!tdb->travlocks.off)
+			return tdb_null;
+		tdb->travlocks.hash = BUCKET(rec.full_hash);
+		if (tdb_lock_record(tdb, tdb->travlocks.off) != 0) {
+			TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_nextkey: lock_record failed (%s)!\n", strerror(errno)));
+			return tdb_null;
+		}
+	}
+	oldhash = tdb->travlocks.hash;
+
+	/* Grab next record: locks chain and returned record,
+	   unlocks old record */
+	if (tdb_next_lock(tdb, &tdb->travlocks, &rec) > 0) {
+		key.dsize = rec.key_len;
+		key.dptr = tdb_alloc_read(tdb, tdb->travlocks.off+sizeof(rec),
+					  key.dsize);
+		/* Unlock the chain of this new record */
+		if (tdb_unlock(tdb, tdb->travlocks.hash, tdb->travlocks.lock_rw) != 0)
+			TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_nextkey: WARNING tdb_unlock failed!\n"));
+	}
+	/* Unlock the chain of old record */
+	if (tdb_unlock(tdb, BUCKET(oldhash), tdb->travlocks.lock_rw) != 0)
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_nextkey: WARNING tdb_unlock failed!\n"));
+	return key;
+}
+
+/* file: dump.c */
+
+static tdb_off_t tdb_dump_record(struct tdb_context *tdb, int hash,
+				 tdb_off_t offset)
+{
+	struct list_struct rec;
+	tdb_off_t tailer_ofs, tailer;
+
+	if (tdb->methods->tdb_read(tdb, offset, (char *)&rec,
+				   sizeof(rec), DOCONV()) == -1) {
+		printf("ERROR: failed to read record at %u\n", offset);
+		return 0;
+	}
+
+	printf(" rec: hash=%d offset=0x%08x next=0x%08x rec_len=%d "
+	       "key_len=%d data_len=%d full_hash=0x%x magic=0x%x\n",
+	       hash, offset, rec.next, rec.rec_len, rec.key_len, rec.data_len,
+	       rec.full_hash, rec.magic);
+
+	tailer_ofs = offset + sizeof(rec) + rec.rec_len - sizeof(tdb_off_t);
+
+	if (tdb_ofs_read(tdb, tailer_ofs, &tailer) == -1) {
+		printf("ERROR: failed to read tailer at %u\n", tailer_ofs);
+		return rec.next;
+	}
+
+	if (tailer != rec.rec_len + sizeof(rec)) {
+		printf("ERROR: tailer does not match record! tailer=%u totalsize=%u\n",
+				(unsigned int)tailer, (unsigned int)(rec.rec_len + sizeof(rec)));
+	}
+	return rec.next;
+}
+
+static int tdb_dump_chain(struct tdb_context *tdb, int i)
+{
+	tdb_off_t rec_ptr, top;
+
+	top = TDB_HASH_TOP(i);
+
+	if (tdb_lock(tdb, i, F_WRLCK) != 0)
+		return -1;
+
+	if (tdb_ofs_read(tdb, top, &rec_ptr) == -1)
+		return tdb_unlock(tdb, i, F_WRLCK);
+
+	if (rec_ptr)
+		printf("hash=%d\n", i);
+
+	while (rec_ptr) {
+		rec_ptr = tdb_dump_record(tdb, i, rec_ptr);
+	}
+
+	return tdb_unlock(tdb, i, F_WRLCK);
+}
+
+void tdb_dump_all(struct tdb_context *tdb)
+{
+	int i;
+	for (i = 0; i < (int)tdb->header.hash_size; i++) {
+		tdb_dump_chain(tdb, i);
+	}
+	printf("freelist:\n");
+	tdb_dump_chain(tdb, -1);
+}
+
+int tdb_printfreelist(struct tdb_context *tdb)
+{
+	int ret;
+	long total_free = 0;
+	tdb_off_t offset, rec_ptr;
+	struct list_struct rec;
+
+	if ((ret = tdb_lock(tdb, -1, F_WRLCK)) != 0)
+		return ret;
+
+	offset = FREELIST_TOP;
+
+	/* read in the freelist top */
+	if (tdb_ofs_read(tdb, offset, &rec_ptr) == -1) {
+		tdb_unlock(tdb, -1, F_WRLCK);
+		return 0;
+	}
+
+	printf("freelist top=[0x%08x]\n", rec_ptr );
+	while (rec_ptr) {
+		if (tdb->methods->tdb_read(tdb, rec_ptr, (char *)&rec,
+					   sizeof(rec), DOCONV()) == -1) {
+			tdb_unlock(tdb, -1, F_WRLCK);
+			return -1;
+		}
+
+		if (rec.magic != TDB_FREE_MAGIC) {
+			printf("bad magic 0x%08x in free list\n", rec.magic);
+			tdb_unlock(tdb, -1, F_WRLCK);
+			return -1;
+		}
+
+		printf("entry offset=[0x%08x], rec.rec_len = [0x%08x (%d)] (end = 0x%08x)\n",
+		       rec_ptr, rec.rec_len, rec.rec_len, rec_ptr + rec.rec_len);
+		total_free += rec.rec_len;
+
+		/* move to the next record */
+		rec_ptr = rec.next;
+	}
+	printf("total rec_len = [0x%08x (%d)]\n", (int)total_free,
+               (int)total_free);
+
+	return tdb_unlock(tdb, -1, F_WRLCK);
+}
+
+/* file: tdb.c */
+
+/*
+  non-blocking increment of the tdb sequence number if the tdb has been opened using
+  the TDB_SEQNUM flag
+*/
+void tdb_increment_seqnum_nonblock(struct tdb_context *tdb)
+{
+	tdb_off_t seqnum=0;
+
+	if (!(tdb->flags & TDB_SEQNUM)) {
+		return;
+	}
+
+	/* we ignore errors from this, as we have no sane way of
+	   dealing with them.
+	*/
+	if (tdb_ofs_read(tdb, TDB_SEQNUM_OFS, &seqnum) == -1)
+		return;
+	seqnum++;
+	(void) tdb_ofs_write(tdb, TDB_SEQNUM_OFS, &seqnum);
+}
+
+/*
+  increment the tdb sequence number if the tdb has been opened using
+  the TDB_SEQNUM flag
+*/
+static void tdb_increment_seqnum(struct tdb_context *tdb)
+{
+	if (!(tdb->flags & TDB_SEQNUM)) {
+		return;
+	}
+
+	if (tdb_brlock(tdb, TDB_SEQNUM_OFS, F_WRLCK, F_SETLKW, 1, 1) != 0) {
+		return;
+	}
+
+	tdb_increment_seqnum_nonblock(tdb);
+
+	tdb_brlock(tdb, TDB_SEQNUM_OFS, F_UNLCK, F_SETLKW, 1, 1);
+}
+
+static int tdb_key_compare(TDB_DATA key, TDB_DATA data,
+			   void *private_data EXT2FS_ATTR((unused)))
+{
+	return memcmp(data.dptr, key.dptr, data.dsize);
+}
+
+/* Returns 0 on fail.  On success, return offset of record, and fills
+   in rec */
+static tdb_off_t tdb_find(struct tdb_context *tdb, TDB_DATA key, u32 hash,
+			struct list_struct *r)
+{
+	tdb_off_t rec_ptr;
+
+	/* read in the hash top */
+	if (tdb_ofs_read(tdb, TDB_HASH_TOP(hash), &rec_ptr) == -1)
+		return 0;
+
+	/* keep looking until we find the right record */
+	while (rec_ptr) {
+		if (tdb_rec_read(tdb, rec_ptr, r) == -1)
+			return 0;
+
+		if (!TDB_DEAD(r) && hash==r->full_hash
+		    && key.dsize==r->key_len
+		    && tdb_parse_data(tdb, key, rec_ptr + sizeof(*r),
+				      r->key_len, tdb_key_compare,
+				      NULL) == 0) {
+			return rec_ptr;
+		}
+		rec_ptr = r->next;
+	}
+	return TDB_ERRCODE(TDB_ERR_NOEXIST, 0);
+}
+
+/* As tdb_find, but if you succeed, keep the lock */
+tdb_off_t tdb_find_lock_hash(struct tdb_context *tdb, TDB_DATA key, u32 hash, int locktype,
+			   struct list_struct *rec)
+{
+	u32 rec_ptr;
+
+	if (tdb_lock(tdb, BUCKET(hash), locktype) == -1)
+		return 0;
+	if (!(rec_ptr = tdb_find(tdb, key, hash, rec)))
+		tdb_unlock(tdb, BUCKET(hash), locktype);
+	return rec_ptr;
+}
+
+
+/* update an entry in place - this only works if the new data size
+   is <= the old data size and the key exists.
+   on failure return -1.
+*/
+static int tdb_update_hash(struct tdb_context *tdb, TDB_DATA key, u32 hash, TDB_DATA dbuf)
+{
+	struct list_struct rec;
+	tdb_off_t rec_ptr;
+
+	/* find entry */
+	if (!(rec_ptr = tdb_find(tdb, key, hash, &rec)))
+		return -1;
+
+	/* must be long enough key, data and tailer */
+	if (rec.rec_len < key.dsize + dbuf.dsize + sizeof(tdb_off_t)) {
+		tdb->ecode = TDB_SUCCESS; /* Not really an error */
+		return -1;
+	}
+
+	if (tdb->methods->tdb_write(tdb, rec_ptr + sizeof(rec) + rec.key_len,
+		      dbuf.dptr, dbuf.dsize) == -1)
+		return -1;
+
+	if (dbuf.dsize != rec.data_len) {
+		/* update size */
+		rec.data_len = dbuf.dsize;
+		return tdb_rec_write(tdb, rec_ptr, &rec);
+	}
+
+	return 0;
+}
+
+/* find an entry in the database given a key */
+/* If an entry doesn't exist tdb_err will be set to
+ * TDB_ERR_NOEXIST. If a key has no data attached
+ * then the TDB_DATA will have zero length but
+ * a non-zero pointer
+ */
+TDB_DATA tdb_fetch(struct tdb_context *tdb, TDB_DATA key)
+{
+	tdb_off_t rec_ptr;
+	struct list_struct rec;
+	TDB_DATA ret;
+	u32 hash;
+
+	/* find which hash bucket it is in */
+	hash = tdb->hash_fn(&key);
+	if (!(rec_ptr = tdb_find_lock_hash(tdb,key,hash,F_RDLCK,&rec)))
+		return tdb_null;
+
+	ret.dptr = tdb_alloc_read(tdb, rec_ptr + sizeof(rec) + rec.key_len,
+				  rec.data_len);
+	ret.dsize = rec.data_len;
+	tdb_unlock(tdb, BUCKET(rec.full_hash), F_RDLCK);
+	return ret;
+}
+
+/*
+ * Find an entry in the database and hand the record's data to a parsing
+ * function. The parsing function is executed under the chain read lock, so it
+ * should be fast and should not block on other syscalls.
+ *
+ * DONT CALL OTHER TDB CALLS FROM THE PARSER, THIS MIGHT LEAD TO SEGFAULTS.
+ *
+ * For mmapped tdb's that do not have a transaction open it points the parsing
+ * function directly at the mmap area, it avoids the malloc/memcpy in this
+ * case. If a transaction is open or no mmap is available, it has to do
+ * malloc/read/parse/free.
+ *
+ * This is interesting for all readers of potentially large data structures in
+ * the tdb records, ldb indexes being one example.
+ */
+
+int tdb_parse_record(struct tdb_context *tdb, TDB_DATA key,
+		     int (*parser)(TDB_DATA key, TDB_DATA data,
+				   void *private_data),
+		     void *private_data)
+{
+	tdb_off_t rec_ptr;
+	struct list_struct rec;
+	int ret;
+	u32 hash;
+
+	/* find which hash bucket it is in */
+	hash = tdb->hash_fn(&key);
+
+	if (!(rec_ptr = tdb_find_lock_hash(tdb,key,hash,F_RDLCK,&rec))) {
+		return TDB_ERRCODE(TDB_ERR_NOEXIST, 0);
+	}
+
+	ret = tdb_parse_data(tdb, key, rec_ptr + sizeof(rec) + rec.key_len,
+			     rec.data_len, parser, private_data);
+
+	tdb_unlock(tdb, BUCKET(rec.full_hash), F_RDLCK);
+
+	return ret;
+}
+
+/* check if an entry in the database exists
+
+   note that 1 is returned if the key is found and 0 is returned if not found
+   this doesn't match the conventions in the rest of this module, but is
+   compatible with gdbm
+*/
+static int tdb_exists_hash(struct tdb_context *tdb, TDB_DATA key, u32 hash)
+{
+	struct list_struct rec;
+
+	if (tdb_find_lock_hash(tdb, key, hash, F_RDLCK, &rec) == 0)
+		return 0;
+	tdb_unlock(tdb, BUCKET(rec.full_hash), F_RDLCK);
+	return 1;
+}
+
+int tdb_exists(struct tdb_context *tdb, TDB_DATA key)
+{
+	u32 hash = tdb->hash_fn(&key);
+	return tdb_exists_hash(tdb, key, hash);
+}
+
+/* actually delete an entry in the database given the offset */
+int tdb_do_delete(struct tdb_context *tdb, tdb_off_t rec_ptr, struct list_struct*rec)
+{
+	tdb_off_t last_ptr, i;
+	struct list_struct lastrec;
+
+	if (tdb->read_only || tdb->traverse_read) return -1;
+
+	if (tdb_write_lock_record(tdb, rec_ptr) == -1) {
+		/* Someone traversing here: mark it as dead */
+		rec->magic = TDB_DEAD_MAGIC;
+		return tdb_rec_write(tdb, rec_ptr, rec);
+	}
+	if (tdb_write_unlock_record(tdb, rec_ptr) != 0)
+		return -1;
+
+	/* find previous record in hash chain */
+	if (tdb_ofs_read(tdb, TDB_HASH_TOP(rec->full_hash), &i) == -1)
+		return -1;
+	for (last_ptr = 0; i != rec_ptr; last_ptr = i, i = lastrec.next)
+		if (tdb_rec_read(tdb, i, &lastrec) == -1)
+			return -1;
+
+	/* unlink it: next ptr is at start of record. */
+	if (last_ptr == 0)
+		last_ptr = TDB_HASH_TOP(rec->full_hash);
+	if (tdb_ofs_write(tdb, last_ptr, &rec->next) == -1)
+		return -1;
+
+	/* recover the space */
+	if (tdb_free(tdb, rec_ptr, rec) == -1)
+		return -1;
+	return 0;
+}
+
+static int tdb_count_dead(struct tdb_context *tdb, u32 hash)
+{
+	int res = 0;
+	tdb_off_t rec_ptr;
+	struct list_struct rec;
+
+	/* read in the hash top */
+	if (tdb_ofs_read(tdb, TDB_HASH_TOP(hash), &rec_ptr) == -1)
+		return 0;
+
+	while (rec_ptr) {
+		if (tdb_rec_read(tdb, rec_ptr, &rec) == -1)
+			return 0;
+
+		if (rec.magic == TDB_DEAD_MAGIC) {
+			res += 1;
+		}
+		rec_ptr = rec.next;
+	}
+	return res;
+}
+
+/*
+ * Purge all DEAD records from a hash chain
+ */
+static int tdb_purge_dead(struct tdb_context *tdb, u32 hash)
+{
+	int res = -1;
+	struct list_struct rec;
+	tdb_off_t rec_ptr;
+
+	if (tdb_lock(tdb, -1, F_WRLCK) == -1) {
+		return -1;
+	}
+
+	/* read in the hash top */
+	if (tdb_ofs_read(tdb, TDB_HASH_TOP(hash), &rec_ptr) == -1)
+		goto fail;
+
+	while (rec_ptr) {
+		tdb_off_t next;
+
+		if (tdb_rec_read(tdb, rec_ptr, &rec) == -1) {
+			goto fail;
+		}
+
+		next = rec.next;
+
+		if (rec.magic == TDB_DEAD_MAGIC
+		    && tdb_do_delete(tdb, rec_ptr, &rec) == -1) {
+			goto fail;
+		}
+		rec_ptr = next;
+	}
+	res = 0;
+ fail:
+	tdb_unlock(tdb, -1, F_WRLCK);
+	return res;
+}
+
+/* delete an entry in the database given a key */
+static int tdb_delete_hash(struct tdb_context *tdb, TDB_DATA key, u32 hash)
+{
+	tdb_off_t rec_ptr;
+	struct list_struct rec;
+	int ret;
+
+	if (tdb->max_dead_records != 0) {
+
+		/*
+		 * Allow for some dead records per hash chain, mainly for
+		 * tdb's with a very high create/delete rate like locking.tdb.
+		 */
+
+		if (tdb_lock(tdb, BUCKET(hash), F_WRLCK) == -1)
+			return -1;
+
+		if (tdb_count_dead(tdb, hash) >= tdb->max_dead_records) {
+			/*
+			 * Don't let the per-chain freelist grow too large,
+			 * delete all existing dead records
+			 */
+			tdb_purge_dead(tdb, hash);
+		}
+
+		if (!(rec_ptr = tdb_find(tdb, key, hash, &rec))) {
+			tdb_unlock(tdb, BUCKET(hash), F_WRLCK);
+			return -1;
+		}
+
+		/*
+		 * Just mark the record as dead.
+		 */
+		rec.magic = TDB_DEAD_MAGIC;
+		ret = tdb_rec_write(tdb, rec_ptr, &rec);
+	}
+	else {
+		if (!(rec_ptr = tdb_find_lock_hash(tdb, key, hash, F_WRLCK,
+						   &rec)))
+			return -1;
+
+		ret = tdb_do_delete(tdb, rec_ptr, &rec);
+	}
+
+	if (ret == 0) {
+		tdb_increment_seqnum(tdb);
+	}
+
+	if (tdb_unlock(tdb, BUCKET(rec.full_hash), F_WRLCK) != 0)
+		TDB_LOG((tdb, TDB_DEBUG_WARNING, "tdb_delete: WARNING tdb_unlock failed!\n"));
+	return ret;
+}
+
+int tdb_delete(struct tdb_context *tdb, TDB_DATA key)
+{
+	u32 hash = tdb->hash_fn(&key);
+	return tdb_delete_hash(tdb, key, hash);
+}
+
+/*
+ * See if we have a dead record around with enough space
+ */
+static tdb_off_t tdb_find_dead(struct tdb_context *tdb, u32 hash,
+			       struct list_struct *r, tdb_len_t length)
+{
+	tdb_off_t rec_ptr;
+
+	/* read in the hash top */
+	if (tdb_ofs_read(tdb, TDB_HASH_TOP(hash), &rec_ptr) == -1)
+		return 0;
+
+	/* keep looking until we find the right record */
+	while (rec_ptr) {
+		if (tdb_rec_read(tdb, rec_ptr, r) == -1)
+			return 0;
+
+		if (TDB_DEAD(r) && r->rec_len >= length) {
+			/*
+			 * First fit for simple coding, TODO: change to best
+			 * fit
+			 */
+			return rec_ptr;
+		}
+		rec_ptr = r->next;
+	}
+	return 0;
+}
+
+/* store an element in the database, replacing any existing element
+   with the same key
+
+   return 0 on success, -1 on failure
+*/
+int tdb_store(struct tdb_context *tdb, TDB_DATA key, TDB_DATA dbuf, int flag)
+{
+	struct list_struct rec;
+	u32 hash;
+	tdb_off_t rec_ptr;
+	char *p = NULL;
+	int ret = -1;
+
+	if (tdb->read_only || tdb->traverse_read) {
+		tdb->ecode = TDB_ERR_RDONLY;
+		return -1;
+	}
+
+	/* find which hash bucket it is in */
+	hash = tdb->hash_fn(&key);
+	if (tdb_lock(tdb, BUCKET(hash), F_WRLCK) == -1)
+		return -1;
+
+	/* check for it existing, on insert. */
+	if (flag == TDB_INSERT) {
+		if (tdb_exists_hash(tdb, key, hash)) {
+			tdb->ecode = TDB_ERR_EXISTS;
+			goto fail;
+		}
+	} else {
+		/* first try in-place update, on modify or replace. */
+		if (tdb_update_hash(tdb, key, hash, dbuf) == 0) {
+			goto done;
+		}
+		if (tdb->ecode == TDB_ERR_NOEXIST &&
+		    flag == TDB_MODIFY) {
+			/* if the record doesn't exist and we are in TDB_MODIFY mode then
+			 we should fail the store */
+			goto fail;
+		}
+	}
+	/* reset the error code potentially set by the tdb_update() */
+	tdb->ecode = TDB_SUCCESS;
+
+	/* delete any existing record - if it doesn't exist we don't
+           care.  Doing this first reduces fragmentation, and avoids
+           coalescing with `allocated' block before it's updated. */
+	if (flag != TDB_INSERT)
+		tdb_delete_hash(tdb, key, hash);
+
+	/* Copy key+value *before* allocating free space in case malloc
+	   fails and we are left with a dead spot in the tdb. */
+
+	if (!(p = (char *)malloc(key.dsize + dbuf.dsize))) {
+		tdb->ecode = TDB_ERR_OOM;
+		goto fail;
+	}
+
+	memcpy(p, key.dptr, key.dsize);
+	if (dbuf.dsize)
+		memcpy(p+key.dsize, dbuf.dptr, dbuf.dsize);
+
+	if (tdb->max_dead_records != 0) {
+		/*
+		 * Allow for some dead records per hash chain, look if we can
+		 * find one that can hold the new record. We need enough space
+		 * for key, data and tailer. If we find one, we don't have to
+		 * consult the central freelist.
+		 */
+		rec_ptr = tdb_find_dead(
+			tdb, hash, &rec,
+			key.dsize + dbuf.dsize + sizeof(tdb_off_t));
+
+		if (rec_ptr != 0) {
+			rec.key_len = key.dsize;
+			rec.data_len = dbuf.dsize;
+			rec.full_hash = hash;
+			rec.magic = TDB_MAGIC;
+			if (tdb_rec_write(tdb, rec_ptr, &rec) == -1
+			    || tdb->methods->tdb_write(
+				    tdb, rec_ptr + sizeof(rec),
+				    p, key.dsize + dbuf.dsize) == -1) {
+				goto fail;
+			}
+			goto done;
+		}
+	}
+
+	/*
+	 * We have to allocate some space from the freelist, so this means we
+	 * have to lock it. Use the chance to purge all the DEAD records from
+	 * the hash chain under the freelist lock.
+	 */
+
+	if (tdb_lock(tdb, -1, F_WRLCK) == -1) {
+		goto fail;
+	}
+
+	if ((tdb->max_dead_records != 0)
+	    && (tdb_purge_dead(tdb, hash) == -1)) {
+		tdb_unlock(tdb, -1, F_WRLCK);
+		goto fail;
+	}
+
+	/* we have to allocate some space */
+	rec_ptr = tdb_allocate(tdb, key.dsize + dbuf.dsize, &rec);
+
+	tdb_unlock(tdb, -1, F_WRLCK);
+
+	if (rec_ptr == 0) {
+		goto fail;
+	}
+
+	/* Read hash top into next ptr */
+	if (tdb_ofs_read(tdb, TDB_HASH_TOP(hash), &rec.next) == -1)
+		goto fail;
+
+	rec.key_len = key.dsize;
+	rec.data_len = dbuf.dsize;
+	rec.full_hash = hash;
+	rec.magic = TDB_MAGIC;
+
+	/* write out and point the top of the hash chain at it */
+	if (tdb_rec_write(tdb, rec_ptr, &rec) == -1
+	    || tdb->methods->tdb_write(tdb, rec_ptr+sizeof(rec), p, key.dsize+dbuf.dsize)==-1
+	    || tdb_ofs_write(tdb, TDB_HASH_TOP(hash), &rec_ptr) == -1) {
+		/* Need to tdb_unallocate() here */
+		goto fail;
+	}
+
+ done:
+	ret = 0;
+ fail:
+	if (ret == 0) {
+		tdb_increment_seqnum(tdb);
+	}
+
+	SAFE_FREE(p);
+	tdb_unlock(tdb, BUCKET(hash), F_WRLCK);
+	return ret;
+}
+
+
+/* Append to an entry. Create if not exist. */
+int tdb_append(struct tdb_context *tdb, TDB_DATA key, TDB_DATA new_dbuf)
+{
+	u32 hash;
+	TDB_DATA dbuf;
+	int ret = -1;
+
+	/* find which hash bucket it is in */
+	hash = tdb->hash_fn(&key);
+	if (tdb_lock(tdb, BUCKET(hash), F_WRLCK) == -1)
+		return -1;
+
+	dbuf = tdb_fetch(tdb, key);
+
+	if (dbuf.dptr == NULL) {
+		dbuf.dptr = (unsigned char *)malloc(new_dbuf.dsize);
+	} else {
+		unsigned char *new_dptr = (unsigned char *)realloc(dbuf.dptr,
+						     dbuf.dsize + new_dbuf.dsize);
+		if (new_dptr == NULL) {
+			free(dbuf.dptr);
+		}
+		dbuf.dptr = new_dptr;
+	}
+
+	if (dbuf.dptr == NULL) {
+		tdb->ecode = TDB_ERR_OOM;
+		goto failed;
+	}
+
+	memcpy(dbuf.dptr + dbuf.dsize, new_dbuf.dptr, new_dbuf.dsize);
+	dbuf.dsize += new_dbuf.dsize;
+
+	ret = tdb_store(tdb, key, dbuf, 0);
+
+failed:
+	tdb_unlock(tdb, BUCKET(hash), F_WRLCK);
+	SAFE_FREE(dbuf.dptr);
+	return ret;
+}
+
+
+/*
+  return the name of the current tdb file
+  useful for external logging functions
+*/
+const char *tdb_name(struct tdb_context *tdb)
+{
+	return tdb->name;
+}
+
+/*
+  return the underlying file descriptor being used by tdb, or -1
+  useful for external routines that want to check the device/inode
+  of the fd
+*/
+int tdb_fd(struct tdb_context *tdb)
+{
+	return tdb->fd;
+}
+
+/*
+  return the current logging function
+  useful for external tdb routines that wish to log tdb errors
+*/
+tdb_log_func tdb_log_fn(struct tdb_context *tdb)
+{
+	return tdb->log.log_fn;
+}
+
+
+/*
+  get the tdb sequence number. Only makes sense if the writers opened
+  with TDB_SEQNUM set. Note that this sequence number will wrap quite
+  quickly, so it should only be used for a 'has something changed'
+  test, not for code that relies on the count of the number of changes
+  made. If you want a counter then use a tdb record.
+
+  The aim of this sequence number is to allow for a very lightweight
+  test of a possible tdb change.
+*/
+int tdb_get_seqnum(struct tdb_context *tdb)
+{
+	tdb_off_t seqnum=0;
+
+	if (tdb_ofs_read(tdb, TDB_SEQNUM_OFS, &seqnum) == -1)
+		return 0;
+	return seqnum;
+}
+
+int tdb_hash_size(struct tdb_context *tdb)
+{
+	return tdb->header.hash_size;
+}
+
+size_t tdb_map_size(struct tdb_context *tdb)
+{
+	return tdb->map_size;
+}
+
+int tdb_get_flags(struct tdb_context *tdb)
+{
+	return tdb->flags;
+}
+
+
+/*
+  enable sequence number handling on an open tdb
+*/
+void tdb_enable_seqnum(struct tdb_context *tdb)
+{
+	tdb->flags |= TDB_SEQNUM;
+}
+
+/* file: open.c */
+
+/* all contexts, to ensure no double-opens (fcntl locks don't nest!) */
+static struct tdb_context *tdbs = NULL;
+
+
+/* This is from a hash algorithm suggested by Rogier Wolff */
+static unsigned int default_tdb_hash(TDB_DATA *key)
+{
+	u32 value;	/* Used to compute the hash value.  */
+	u32   i;	/* Used to cycle through random values. */
+
+	/* Set the initial value from the key size. */
+	for (value = 0, i=0; i < key->dsize; i++)
+		value = value * 256 + key->dptr[i] + (value >> 24) * 241;
+
+	return value;
+}
+
+
+/* initialise a new database with a specified hash size */
+static int tdb_new_database(struct tdb_context *tdb, int hash_size)
+{
+	struct tdb_header *newdb;
+	int size, 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)))
+		return TDB_ERRCODE(TDB_ERR_OOM, -1);
+
+	/* Fill in the header */
+	newdb->version = TDB_VERSION;
+	newdb->hash_size = hash_size;
+	if (tdb->flags & TDB_INTERNAL) {
+		tdb->map_size = size;
+		tdb->map_ptr = (char *)newdb;
+		memcpy(&tdb->header, newdb, sizeof(tdb->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(&tdb->header, newdb, sizeof(tdb->header));
+	/* Don't endian-convert the magic food! */
+	memcpy(newdb->magic_food, TDB_MAGIC_FOOD, strlen(TDB_MAGIC_FOOD)+1);
+	if (write(tdb->fd, newdb, size) != size) {
+		ret = -1;
+	} else {
+		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. */
+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 EXT2FS_ATTR((unused)),
+			enum tdb_debug_level level EXT2FS_ATTR((unused)),
+			const char *fmt EXT2FS_ATTR((unused)), ...)
+{
+}
+
+
+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)
+{
+	struct tdb_context *tdb;
+	struct stat st;
+	int rev = 0, locked = 0;
+	unsigned char *vp;
+	u32 vertest;
+
+	if (!(tdb = (struct tdb_context *)calloc(1, sizeof *tdb))) {
+		/* Can't log this */
+		errno = ENOMEM;
+		goto fail;
+	}
+	tdb_io_init(tdb);
+	tdb->fd = -1;
+	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;
+	}
+	tdb->hash_fn = hash_fn ? hash_fn : default_tdb_hash;
+
+	/* cache the page size */
+	tdb->page_size = sysconf(_SC_PAGESIZE);
+	if (tdb->page_size <= 0) {
+		tdb->page_size = 0x2000;
+	}
+
+	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;
+	}
+
+	/* 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, hash_size) != 0) {
+			TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_open_ex: tdb_new_database failed!"));
+			goto fail;
+		}
+		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) */
+	}
+
+	/* ensure there is only one process initialising at once */
+	if (tdb->methods->tdb_brlock(tdb, GLOBAL_LOCK, F_WRLCK, F_SETLKW, 0, 1) == -1) {
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_open_ex: failed to get global 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) &&
+	    (locked = (tdb->methods->tdb_brlock(tdb, ACTIVE_LOCK, F_WRLCK, F_SETLK, 0, 1) == 0))) {
+		open_flags |= O_CREAT;
+		if (ftruncate(tdb->fd, 0) == -1) {
+			TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_open_ex: "
+				 "failed to truncate %s: %s\n",
+				 name, strerror(errno)));
+			goto fail; /* errno set by ftruncate */
+		}
+	}
+
+	if (read(tdb->fd, &tdb->header, sizeof(tdb->header)) != sizeof(tdb->header)
+	    || memcmp(tdb->header.magic_food, TDB_MAGIC_FOOD,
+		      sizeof(TDB_MAGIC_FOOD)) != 0
+	    || (tdb->header.version != TDB_VERSION
+		&& !(rev = (tdb->header.version==TDB_BYTEREV(TDB_VERSION))))) {
+		/* its not a valid database - possibly initialise it */
+		if (!(open_flags & O_CREAT) || tdb_new_database(tdb, hash_size) == -1) {
+			errno = EIO; /* ie bad format or something */
+			goto fail;
+		}
+		rev = (tdb->flags & TDB_CONVERT);
+	}
+	vp = (unsigned char *)&tdb->header.version;
+	vertest = (((u32)vp[0]) << 24) | (((u32)vp[1]) << 16) |
+		  (((u32)vp[2]) << 8) | (u32)vp[3];
+	tdb->flags |= (vertest==TDB_VERSION) ? TDB_BIGENDIAN : 0;
+	if (!rev)
+		tdb->flags &= ~TDB_CONVERT;
+	else {
+		tdb->flags |= TDB_CONVERT;
+		tdb_convert(&tdb->header, sizeof(tdb->header));
+	}
+	if (fstat(tdb->fd, &st) == -1)
+		goto fail;
+
+	if (tdb->header.rwlocks != 0) {
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_open_ex: spinlocks no longer supported\n"));
+		goto fail;
+	}
+
+	/* Is it already in the open list?  If so, fail. */
+	if (tdb_already_open(st.st_dev, st.st_ino)) {
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_open_ex: "
+			 "%s (%d,%d) is already open in this process\n",
+			 name, (int)st.st_dev, (int)st.st_ino));
+		errno = EBUSY;
+		goto fail;
+	}
+
+	if (!(tdb->name = (char *)strdup(name))) {
+		errno = ENOMEM;
+		goto fail;
+	}
+
+	tdb->map_size = st.st_size;
+	tdb->device = st.st_dev;
+	tdb->inode = st.st_ino;
+	tdb->max_dead_records = 0;
+	tdb_mmap(tdb);
+	if (locked) {
+		if (tdb->methods->tdb_brlock(tdb, ACTIVE_LOCK, F_UNLCK, F_SETLK, 0, 1) == -1) {
+			TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_open_ex: "
+				 "failed to take 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->methods->tdb_brlock(tdb, ACTIVE_LOCK, F_RDLCK, F_SETLKW, 0, 1) == -1)
+			goto fail;
+	}
+
+	/* if needed, run recovery */
+	if (tdb_transaction_recover(tdb) == -1) {
+		goto fail;
+	}
+
+ internal:
+	/* Internal (memory-only) databases skip all the code above to
+	 * do with disk files, and resume here by releasing their
+	 * global lock and hooking into the active list. */
+	if (tdb->methods->tdb_brlock(tdb, GLOBAL_LOCK, F_UNLCK, F_SETLKW, 0, 1) == -1)
+		goto fail;
+	tdb->next = tdbs;
+	tdbs = tdb;
+	return tdb;
+
+ fail:
+	{ int save_errno = errno;
+
+	if (!tdb)
+		return NULL;
+
+	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)
+		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);
+	errno = save_errno;
+	return NULL;
+	}
+}
+
+/*
+ * Set the maximum number of dead records per hash chain
+ */
+
+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.
+ **/
+int tdb_close(struct tdb_context *tdb)
+{
+	struct tdb_context **i;
+	int ret = 0;
+
+	if (tdb->transaction) {
+		tdb_transaction_cancel(tdb);
+	}
+
+	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);
+	SAFE_FREE(tdb->lockrecs);
+
+	/* Remove from contexts list */
+	for (i = &tdbs; *i; i = &(*i)->next) {
+		if (*i == tdb) {
+			*i = tdb->next;
+			break;
+		}
+	}
+
+	memset(tdb, 0, sizeof(*tdb));
+	SAFE_FREE(tdb);
+
+	return ret;
+}
+
+/* register a logging function */
+void tdb_set_logging_function(struct tdb_context *tdb,
+                              const struct tdb_logging_context *log_ctx)
+{
+        tdb->log = *log_ctx;
+}
+
+void *tdb_get_logging_private(struct tdb_context *tdb)
+{
+	return tdb->log.log_private;
+}
+
+/* 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 */
+int tdb_reopen(struct tdb_context *tdb)
+{
+	struct stat st;
+
+	if (tdb->flags & TDB_INTERNAL) {
+		return 0; /* Nothing to do. */
+	}
+
+	if (tdb->num_locks != 0 || tdb->global_lock.count) {
+		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 (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;
+	}
+	if ((tdb->flags & TDB_CLEAR_IF_FIRST) &&
+	    (tdb->methods->tdb_brlock(tdb, ACTIVE_LOCK, F_RDLCK, F_SETLKW, 0, 1) == -1)) {
+		TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_reopen: failed to obtain active lock\n"));
+		goto fail;
+	}
+	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;
+	}
+	tdb_mmap(tdb);
+
+	return 0;
+
+fail:
+	tdb_close(tdb);
+	return -1;
+}
+
+/* reopen all tdb's */
+int tdb_reopen_all(int parent_longlived)
+{
+	struct tdb_context *tdb;
+
+	for (tdb=tdbs; tdb; tdb = tdb->next) {
+		/*
+		 * 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. */
+			tdb->flags &= ~TDB_CLEAR_IF_FIRST;
+		}
+
+		if (tdb_reopen(tdb) != 0)
+			return -1;
+	}
+
+	return 0;
+}
+
+/**
+ * Flush a database file from the page cache.
+ **/
+int tdb_flush(struct tdb_context *tdb)
+{
+	if (tdb->fd != -1)
+		return fsync(tdb->fd);
+	return 0;
+}