/*

   Unix SMB/CIFS implementation.

   trivial database library

   Copyright (C) Andrew Tridgell              1999-2005

   Copyright (C) Paul `Rusty' Russell		   2000

   Copyright (C) Jeremy Allison			   2000-2003

     ** NOTE! The following LGPL license applies to the tdb

     ** library. This does NOT imply that all of Samba is released

     ** under the LGPL

   This library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 3 of the License, or (at your option) any later version.

   This library is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with this library; if not, see <http://www.gnu.org/licenses/>.

*/

#include "tdb_private.h"

_PUBLIC_ void tdb_setalarm_sigptr(struct tdb_context *tdb, volatile sig_atomic_t *ptr)

{

	tdb->interrupt_sig_ptr = ptr;

}

static int fcntl_lock(struct tdb_context *tdb,

		      int rw, off_t off, off_t len, bool waitflag)

{

	struct flock fl;

	int cmd;

#ifdef USE_TDB_MUTEX_LOCKING

	{

		int ret;

		if (tdb_mutex_lock(tdb, rw, off, len, waitflag, &ret)) {

			return ret;

		}

	}

#endif

	fl.l_type = rw;

	fl.l_whence = SEEK_SET;

	fl.l_start = off;

	fl.l_len = len;

	fl.l_pid = 0;

	cmd = waitflag ? F_SETLKW : F_SETLK;

	return fcntl(tdb->fd, cmd, &fl);

}

static int fcntl_unlock(struct tdb_context *tdb, int rw, off_t off, off_t len)

{

	struct flock fl;

#if 0 /* Check they matched up locks and unlocks correctly. */

	char line[80];

	FILE *locks;

	bool found = false;

	locks = fopen("/proc/locks", "r");

	while (fgets(line, 80, locks)) {

		char *p;

		int type, start, l;

		/* eg. 1: FLOCK  ADVISORY  WRITE 2440 08:01:2180826 0 EOF */

		p = strchr(line, ':') + 1;

		if (strncmp(p, " POSIX  ADVISORY  ", strlen(" POSIX  ADVISORY  ")))

			continue;

		p += strlen(" FLOCK  ADVISORY  ");

		if (strncmp(p, "READ  ", strlen("READ  ")) == 0)

			type = F_RDLCK;

		else if (strncmp(p, "WRITE ", strlen("WRITE ")) == 0)

			type = F_WRLCK;

		else

			abort();

		p += 6;

		if (atoi(p) != getpid())

			continue;

		p = strchr(strchr(p, ' ') + 1, ' ') + 1;

		start = atoi(p);

		p = strchr(p, ' ') + 1;

		if (strncmp(p, "EOF", 3) == 0)

			l = 0;

		else

			l = atoi(p) - start + 1;

		if (off == start) {

			if (len != l) {

				fprintf(stderr, "Len %u should be %u: %s",

					(int)len, l, line);

				abort();

			}

			if (type != rw) {

				fprintf(stderr, "Type %s wrong: %s",

					rw == F_RDLCK ? "READ" : "WRITE", line);

				abort();

			}

			found = true;

			break;

		}

	}

	if (!found) {

		fprintf(stderr, "Unlock on %u@%u not found!\n",

			(int)off, (int)len);

		abort();

	}

	fclose(locks);

#endif

#ifdef USE_TDB_MUTEX_LOCKING

	{

		int ret;

		if (tdb_mutex_unlock(tdb, rw, off, len, &ret)) {

			return ret;

		}

	}

#endif

	fl.l_type = F_UNLCK;

	fl.l_whence = SEEK_SET;

	fl.l_start = off;

	fl.l_len = len;

	fl.l_pid = 0;

	return fcntl(tdb->fd, F_SETLKW, &fl);

}

/*

 * Calculate the lock offset for a list

 *

 * list -1 is the freelist, otherwise a hash chain.

 *

 * Note that we consistently (but without real reason) lock hash chains at an

 * offset that is 4 bytes below the real offset of the corresponding list head

 * in the db.

 *

 * This is the memory layout of the hashchain array:

 *

 * FREELIST_TOP + 0 = freelist

 * FREELIST_TOP + 4 = hashtable list 0

 * FREELIST_TOP + 8 = hashtable list 1

 * ...

 *

 * Otoh lock_offset computes:

 *

 * freelist = FREELIST_TOP - 4

 * list 0   = FREELIST_TOP + 0

 * list 1   = FREELIST_TOP + 4

 * ...

 *

 * Unfortunately we can't change this calculation in order to align the locking

 * offset with the memory layout, as that would make the locking incompatible

 * between different tdb versions.

 */

static tdb_off_t lock_offset(int list)

{

	return FREELIST_TOP + 4*list;

}

/* a byte range locking function - return 0 on success

   this functions locks/unlocks "len" 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,

	       int rw_type, tdb_off_t offset, size_t len,

	       enum tdb_lock_flags flags)

{

	int ret;

	if (tdb->flags & TDB_NOLOCK) {

		return 0;

	}

	if (flags & TDB_LOCK_MARK_ONLY) {

		return 0;

	}

	if ((rw_type == F_WRLCK) && (tdb->read_only || tdb->traverse_read)) {

		tdb->ecode = TDB_ERR_RDONLY;

		return -1;

	}

	do {

		ret = fcntl_lock(tdb, rw_type, offset, len,

				 flags & TDB_LOCK_WAIT);

		/* Check for a sigalarm break. */

		if (ret == -1 && errno == EINTR &&

				tdb->interrupt_sig_ptr &&

				*tdb->interrupt_sig_ptr) {

			break;

		}

	} while (ret == -1 && errno == EINTR);

	if (ret == -1) {

		tdb->ecode = TDB_ERR_LOCK;

		/* Generic lock error. errno set by fcntl.

		 * EAGAIN is an expected return from non-blocking

		 * locks. */

		if (!(flags & TDB_LOCK_PROBE) && errno != EAGAIN) {

			TDB_LOG((tdb, TDB_DEBUG_TRACE,"tdb_brlock failed (fd=%d) at offset %u rw_type=%d flags=%d len=%zu\n",

				 tdb->fd, offset, rw_type, flags, len));

		}

		return -1;

	}

	return 0;

}

int tdb_brunlock(struct tdb_context *tdb,

		 int rw_type, tdb_off_t offset, size_t len)

{

	int ret;

	if (tdb->flags & TDB_NOLOCK) {

		return 0;

	}

	do {

		ret = fcntl_unlock(tdb, rw_type, offset, len);

	} while (ret == -1 && errno == EINTR);

	if (ret == -1) {

		TDB_LOG((tdb, TDB_DEBUG_TRACE,"tdb_brunlock failed (fd=%d) at offset %u rw_type=%u len=%zu\n",

			 tdb->fd, offset, rw_type, len));

	}

	return ret;

}

/*

 * Do a tdb_brlock in a loop. 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.

 */

static int tdb_brlock_retry(struct tdb_context *tdb,

			    int rw_type, tdb_off_t offset, size_t len,

			    enum tdb_lock_flags flags)

{

	int count = 1000;

	while (count--) {

		struct timeval tv;

		int ret;

		ret = tdb_brlock(tdb, rw_type, offset, len, flags);

		if (ret == 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;;

	}

	return -1;

}

/*

  upgrade a read lock to a write lock.

*/

int tdb_allrecord_upgrade(struct tdb_context *tdb)

{

	int ret;

	if (tdb->allrecord_lock.count != 1) {

		TDB_LOG((tdb, TDB_DEBUG_ERROR,

			 "tdb_allrecord_upgrade failed: count %u too high\n",

			 tdb->allrecord_lock.count));

		tdb->ecode = TDB_ERR_LOCK;

		return -1;

	}

	if (tdb->allrecord_lock.off != 1) {

		TDB_LOG((tdb, TDB_DEBUG_ERROR,

			 "tdb_allrecord_upgrade failed: already upgraded?\n"));

		tdb->ecode = TDB_ERR_LOCK;

		return -1;

	}

	if (tdb_have_mutexes(tdb)) {

		ret = tdb_mutex_allrecord_upgrade(tdb);

		if (ret == -1) {

			goto fail;

		}

		ret = tdb_brlock_retry(tdb, F_WRLCK, lock_offset(tdb->hash_size),

				       0, TDB_LOCK_WAIT|TDB_LOCK_PROBE);

		if (ret == -1) {

			tdb_mutex_allrecord_downgrade(tdb);

		}

	} else {

		ret = tdb_brlock_retry(tdb, F_WRLCK, FREELIST_TOP, 0,

				       TDB_LOCK_WAIT|TDB_LOCK_PROBE);

	}

	if (ret == 0) {

		tdb->allrecord_lock.ltype = F_WRLCK;

		tdb->allrecord_lock.off = 0;

		return 0;

	}

fail:

	TDB_LOG((tdb, TDB_DEBUG_TRACE,"tdb_allrecord_upgrade failed\n"));

	return -1;

}

static struct tdb_lock_type *find_nestlock(struct tdb_context *tdb,

					   tdb_off_t offset)

{

	int i;

	for (i=0; i<tdb->num_lockrecs; i++) {

		if (tdb->lockrecs[i].off == offset) {

			return &tdb->lockrecs[i];

		}

	}

	return NULL;

}

/* lock an offset in the database. */

int tdb_nest_lock(struct tdb_context *tdb, uint32_t offset, int ltype,

		  enum tdb_lock_flags flags)

{

	struct tdb_lock_type *new_lck;

	if (offset >= lock_offset(tdb->hash_size)) {

		tdb->ecode = TDB_ERR_LOCK;

		TDB_LOG((tdb, TDB_DEBUG_ERROR,"tdb_lock: invalid offset %u for ltype=%d\n",

			 offset, ltype));

		return -1;

	}

	if (tdb->flags & TDB_NOLOCK)

		return 0;

	new_lck = find_nestlock(tdb, offset);

	if (new_lck) {

		if ((new_lck->ltype == F_RDLCK) && (ltype == F_WRLCK)) {

			if (!tdb_have_mutexes(tdb)) {

				int ret;

				/*

				 * Upgrade the underlying fcntl

				 * lock. Mutexes don't do readlocks,

				 * so this only applies to fcntl

				 * locking.

				 */

				ret = tdb_brlock(tdb, ltype, offset, 1, flags);

				if (ret != 0) {

					return ret;

				}

			}

			new_lck->ltype = F_WRLCK;

		}

		/*

		 * Just increment the in-memory struct, posix locks

		 * don't stack.

		 */

		new_lck->count++;

		return 0;

	}

	if (tdb->num_lockrecs == tdb->lockrecs_array_length) {

		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_array_length = tdb->num_lockrecs+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 (tdb_brlock(tdb, ltype, offset, 1, flags)) {

		return -1;

	}

	new_lck = &tdb->lockrecs[tdb->num_lockrecs];

	new_lck->off = offset;

	new_lck->count = 1;

	new_lck->ltype = ltype;

	tdb->num_lockrecs++;

	return 0;

}

static int tdb_lock_and_recover(struct tdb_context *tdb)

{

	int ret;

	/* We need to match locking order in transaction commit. */

	if (tdb_brlock(tdb, F_WRLCK, FREELIST_TOP, 0, TDB_LOCK_WAIT)) {

		return -1;

	}

	if (tdb_brlock(tdb, F_WRLCK, OPEN_LOCK, 1, TDB_LOCK_WAIT)) {

		tdb_brunlock(tdb, F_WRLCK, FREELIST_TOP, 0);

		return -1;

	}

	ret = tdb_transaction_recover(tdb);

	tdb_brunlock(tdb, F_WRLCK, OPEN_LOCK, 1);

	tdb_brunlock(tdb, F_WRLCK, FREELIST_TOP, 0);

	return ret;

}

static bool have_data_locks(const struct tdb_context *tdb)

{

	int i;

	for (i = 0; i < tdb->num_lockrecs; i++) {

		if (tdb->lockrecs[i].off >= lock_offset(-1))

			return true;

	}

	return false;

}

/*

 * A allrecord lock allows us to avoid per chain locks. Check if the allrecord

 * lock is strong enough.

 */

static int tdb_lock_covered_by_allrecord_lock(struct tdb_context *tdb,

					      int ltype)

{

	if (ltype == F_RDLCK) {

		/*

		 * The allrecord_lock is equal (F_RDLCK) or stronger

		 * (F_WRLCK). Pass.

		 */

		return 0;

	}

	if (tdb->allrecord_lock.ltype == F_RDLCK) {

		/*

		 * We ask for ltype==F_WRLCK, but the allrecord_lock

		 * is too weak. We can't upgrade here, so fail.

		 */

		tdb->ecode = TDB_ERR_LOCK;

		return -1;

	}

	/*

	 * Asking for F_WRLCK, allrecord is F_WRLCK as well. Pass.

	 */

	return 0;

}

static int tdb_lock_list(struct tdb_context *tdb, int list, int ltype,

			 enum tdb_lock_flags waitflag)

{

	int ret;

	bool check = false;

	if (tdb->allrecord_lock.count) {

		return tdb_lock_covered_by_allrecord_lock(tdb, ltype);

	}

	/*

	 * Check for recoveries: Someone might have kill -9'ed a process

	 * during a commit.

	 */

	check = !have_data_locks(tdb);

	ret = tdb_nest_lock(tdb, lock_offset(list), ltype, waitflag);

	if (ret == 0 && check && tdb_needs_recovery(tdb)) {

		tdb_nest_unlock(tdb, lock_offset(list), ltype, false);

		if (tdb_lock_and_recover(tdb) == -1) {

			return -1;

		}

		return tdb_lock_list(tdb, list, ltype, waitflag);

	}

	return ret;

}

/* 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_list(tdb, list, ltype, TDB_LOCK_WAIT);

	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 */

_PUBLIC_ int tdb_lock_nonblock(struct tdb_context *tdb, int list, int ltype)

{

	return tdb_lock_list(tdb, list, ltype, TDB_LOCK_NOWAIT);

}

int tdb_nest_unlock(struct tdb_context *tdb, uint32_t offset, int ltype,

		    bool mark_lock)

{

	int ret = -1;

	struct tdb_lock_type *lck;

	if (tdb->flags & TDB_NOLOCK)

		return 0;

	/* Sanity checks */

	if (offset >= lock_offset(tdb->hash_size)) {

		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: offset %u invalid (%d)\n", offset, tdb->hash_size));

		return ret;

	}

	lck = find_nestlock(tdb, offset);

	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_brunlock(tdb, ltype, offset, 1);

	}

	/*

	 * Shrink the array by overwriting the element just unlocked with the

	 * last array element.

	 */

	*lck = tdb->lockrecs[--tdb->num_lockrecs];

	/*

	 * 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 (ret)

		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: An error occurred unlocking!\n"));

	return ret;

}

_PUBLIC_ int tdb_unlock(struct tdb_context *tdb, int list, int ltype)

{

	/* a global lock allows us to avoid per chain locks */

	if (tdb->allrecord_lock.count) {

		return tdb_lock_covered_by_allrecord_lock(tdb, ltype);

	}

	return tdb_nest_unlock(tdb, lock_offset(list), ltype, false);

}

/*

  get the transaction lock

 */

int tdb_transaction_lock(struct tdb_context *tdb, int ltype,

			 enum tdb_lock_flags lockflags)

{

	return tdb_nest_lock(tdb, TRANSACTION_LOCK, ltype, lockflags);

}

/*

  release the transaction lock

 */

int tdb_transaction_unlock(struct tdb_context *tdb, int ltype)

{

	return tdb_nest_unlock(tdb, TRANSACTION_LOCK, ltype, false);

}

/* Returns 0 if all done, -1 if error, 1 if ok. */

static int tdb_allrecord_check(struct tdb_context *tdb, int ltype,

			       enum tdb_lock_flags flags, bool upgradable)

{

	/* There are no locks on read-only dbs */

	if (tdb->read_only || tdb->traverse_read) {

		tdb->ecode = TDB_ERR_LOCK;

		return -1;

	}

	if (tdb->allrecord_lock.count &&

	    tdb->allrecord_lock.ltype == (uint32_t)ltype) {

		tdb->allrecord_lock.count++;

		return 0;

	}

	if (tdb->allrecord_lock.count) {

		/* a global lock of a different type exists */

		tdb->ecode = TDB_ERR_LOCK;

		return -1;

	}

	if (tdb_have_extra_locks(tdb)) {

		/* can't combine global and chain locks */

		tdb->ecode = TDB_ERR_LOCK;

		return -1;

	}

	if (upgradable && ltype != F_RDLCK) {

		/* tdb error: you can't upgrade a write lock! */

		tdb->ecode = TDB_ERR_LOCK;

		return -1;

	}

	return 1;

}

/* We only need to lock individual bytes, but Linux merges consecutive locks

 * so we lock in contiguous ranges. */

static int tdb_chainlock_gradual(struct tdb_context *tdb,

				 int ltype, enum tdb_lock_flags flags,

				 size_t off, size_t len)

{

	int ret;

	enum tdb_lock_flags nb_flags = (flags & ~TDB_LOCK_WAIT);

	if (len <= 4) {

		/* Single record.  Just do blocking lock. */

		return tdb_brlock(tdb, ltype, off, len, flags);

	}

	/* First we try non-blocking. */

	ret = tdb_brlock(tdb, ltype, off, len, nb_flags);

	if (ret == 0) {

		return 0;

	}

	/* Try locking first half, then second. */

	ret = tdb_chainlock_gradual(tdb, ltype, flags, off, len / 2);

	if (ret == -1)

		return -1;

	ret = tdb_chainlock_gradual(tdb, ltype, flags,

				    off + len / 2, len - len / 2);

	if (ret == -1) {

		tdb_brunlock(tdb, ltype, off, len / 2);

		return -1;

	}

	return 0;

}

/* lock/unlock entire database.  It can only be upgradable if you have some

 * other way of guaranteeing exclusivity (ie. transaction write lock).

 * We do the locking gradually to avoid being starved by smaller locks. */

int tdb_allrecord_lock(struct tdb_context *tdb, int ltype,

		       enum tdb_lock_flags flags, bool upgradable)

{

	int ret;

	switch (tdb_allrecord_check(tdb, ltype, flags, upgradable)) {

	case -1:

		return -1;

	case 0:

		return 0;

	}

	/* We cover two kinds of locks:

	 * 1) Normal chain locks.  Taken for almost all operations.

	 * 2) Individual records locks.  Taken after normal or free

	 *    chain locks.

	 *

	 * It is (1) which cause the starvation problem, so we're only

	 * gradual for that. */

	if (tdb_have_mutexes(tdb)) {

		ret = tdb_mutex_allrecord_lock(tdb, ltype, flags);

	} else {

		ret = tdb_chainlock_gradual(tdb, ltype, flags, FREELIST_TOP,

					    tdb->hash_size * 4);

	}

	if (ret == -1) {

		return -1;

	}

	/* Grab individual record locks. */

	if (tdb_brlock(tdb, ltype, lock_offset(tdb->hash_size), 0,

		       flags) == -1) {

		if (tdb_have_mutexes(tdb)) {

			tdb_mutex_allrecord_unlock(tdb);

		} else {

			tdb_brunlock(tdb, ltype, FREELIST_TOP,

				     tdb->hash_size * 4);

		}

		return -1;

	}

	tdb->allrecord_lock.count = 1;

	/* If it's upgradable, it's actually exclusive so we can treat

	 * it as a write lock. */

	tdb->allrecord_lock.ltype = upgradable ? F_WRLCK : ltype;

	tdb->allrecord_lock.off = upgradable;

	if (tdb_needs_recovery(tdb)) {

		bool mark = flags & TDB_LOCK_MARK_ONLY;

		tdb_allrecord_unlock(tdb, ltype, mark);

		if (mark) {

			tdb->ecode = TDB_ERR_LOCK;

			TDB_LOG((tdb, TDB_DEBUG_ERROR,

				 "tdb_lockall_mark cannot do recovery\n"));

			return -1;

		}

		if (tdb_lock_and_recover(tdb) == -1) {

			return -1;

		}

		return tdb_allrecord_lock(tdb, ltype, flags, upgradable);

	}

	return 0;

}

/* unlock entire db */

int tdb_allrecord_unlock(struct tdb_context *tdb, int ltype, bool mark_lock)

{

	/* There are no locks on read-only dbs */

	if (tdb->read_only || tdb->traverse_read) {

		tdb->ecode = TDB_ERR_LOCK;

		return -1;

	}

	if (tdb->allrecord_lock.count == 0) {

		tdb->ecode = TDB_ERR_LOCK;

		return -1;

	}

	/* Upgradable locks are marked as write locks. */

	if (tdb->allrecord_lock.ltype != (uint32_t)ltype

	    && (!tdb->allrecord_lock.off || ltype != F_RDLCK)) {

		tdb->ecode = TDB_ERR_LOCK;

		return -1;

	}

	if (tdb->allrecord_lock.count > 1) {

		tdb->allrecord_lock.count--;

		return 0;

	}

	if (!mark_lock) {

		int ret;

		if (tdb_have_mutexes(tdb)) {

			ret = tdb_mutex_allrecord_unlock(tdb);

			if (ret == 0) {

				ret = tdb_brunlock(tdb, ltype,

						   lock_offset(tdb->hash_size),

						   0);

			}

		} else {

			ret = tdb_brunlock(tdb, ltype, FREELIST_TOP, 0);

		}

		if (ret != 0) {

			TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlockall failed "

				 "(%s)\n", strerror(errno)));

			return -1;

		}

	}

	tdb->allrecord_lock.count = 0;

	tdb->allrecord_lock.ltype = 0;

	return 0;

}

/* lock entire database with write lock */

_PUBLIC_ int tdb_lockall(struct tdb_context *tdb)

{

	tdb_trace(tdb, "tdb_lockall");

	return tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_WAIT, false);

}

/* lock entire database with write lock - mark only */

_PUBLIC_ int tdb_lockall_mark(struct tdb_context *tdb)

{

	tdb_trace(tdb, "tdb_lockall_mark");

	return tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_MARK_ONLY, false);

}

/* unlock entire database with write lock - unmark only */

_PUBLIC_ int tdb_lockall_unmark(struct tdb_context *tdb)

{

	tdb_trace(tdb, "tdb_lockall_unmark");

	return tdb_allrecord_unlock(tdb, F_WRLCK, true);

}

/* lock entire database with write lock - nonblocking varient */

_PUBLIC_ int tdb_lockall_nonblock(struct tdb_context *tdb)

{

	int ret = tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_NOWAIT, false);

	tdb_trace_ret(tdb, "tdb_lockall_nonblock", ret);

	return ret;

}

/* unlock entire database with write lock */

_PUBLIC_ int tdb_unlockall(struct tdb_context *tdb)

{

	tdb_trace(tdb, "tdb_unlockall");

	return tdb_allrecord_unlock(tdb, F_WRLCK, false);

}

/* lock entire database with read lock */

_PUBLIC_ int tdb_lockall_read(struct tdb_context *tdb)

{

	tdb_trace(tdb, "tdb_lockall_read");

	return tdb_allrecord_lock(tdb, F_RDLCK, TDB_LOCK_WAIT, false);

}

/* lock entire database with read lock - nonblock varient */

_PUBLIC_ int tdb_lockall_read_nonblock(struct tdb_context *tdb)

{

	int ret = tdb_allrecord_lock(tdb, F_RDLCK, TDB_LOCK_NOWAIT, false);

	tdb_trace_ret(tdb, "tdb_lockall_read_nonblock", ret);

	return ret;

}

/* unlock entire database with read lock */

_PUBLIC_ int tdb_unlockall_read(struct tdb_context *tdb)

{

	tdb_trace(tdb, "tdb_unlockall_read");

	return tdb_allrecord_unlock(tdb, F_RDLCK, false);

}

/* lock/unlock one hash chain. This is meant to be used to reduce

   contention - it cannot guarantee how many records will be locked */

_PUBLIC_ int tdb_chainlock(struct tdb_context *tdb, TDB_DATA key)

{

	int ret = tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);

	tdb_trace_1rec(tdb, "tdb_chainlock", key);

	return ret;

}

/* 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 */

_PUBLIC_ int tdb_chainlock_nonblock(struct tdb_context *tdb, TDB_DATA key)

{

	int ret = tdb_lock_nonblock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);

	tdb_trace_1rec_ret(tdb, "tdb_chainlock_nonblock", key, ret);

	return ret;

}

/* mark a chain as locked without actually locking it. Warning! use with great caution! */

_PUBLIC_ int tdb_chainlock_mark(struct tdb_context *tdb, TDB_DATA key)

{

	int ret = tdb_nest_lock(tdb, lock_offset(BUCKET(tdb->hash_fn(&key))),

				F_WRLCK, TDB_LOCK_MARK_ONLY);

	tdb_trace_1rec(tdb, "tdb_chainlock_mark", key);

	return ret;

}

/* unmark a chain as locked without actually locking it. Warning! use with great caution! */

_PUBLIC_ int tdb_chainlock_unmark(struct tdb_context *tdb, TDB_DATA key)

{