text: /*
     Unix SMB/CIFS implementation.
     global locks based on dbwrap and messaging
     Copyright (C) 2009 by Volker Lendecke
  
     This program is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
     the Free Software Foundation; either version 3 of the License, or
     (at your option) any later version.
  
     This program 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 General Public License for more details.
  
     You should have received a copy of the GNU General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
  
  #include "includes.h"
  #include "g_lock.h"
  
  static NTSTATUS g_lock_force_unlock(struct g_lock_ctx *ctx, const char *name,
  				    struct server_id pid);
  
  struct g_lock_ctx {
  	struct db_context *db;
  	struct messaging_context *msg;
  };
  
  /*
   * The "g_lock.tdb" file contains records, indexed by the 0-terminated
   * lockname. The record contains an array of "struct g_lock_rec"
   * structures. Waiters have the lock_type with G_LOCK_PENDING or'ed.
   */
  
  struct g_lock_rec {
  	enum g_lock_type lock_type;
  	struct server_id pid;
  };
  
  struct g_lock_ctx *g_lock_ctx_init(TALLOC_CTX *mem_ctx,
  				   struct messaging_context *msg)
  {
  	struct g_lock_ctx *result;
  
  	result = talloc(mem_ctx, struct g_lock_ctx);
  	if (result == NULL) {
  		return NULL;
  	}
  	result->msg = msg;
  
  	result->db = db_open(result, lock_path("g_lock.tdb"), 0,
  			     TDB_CLEAR_IF_FIRST, O_RDWR|O_CREAT, 0700);
  	if (result->db == NULL) {
  		DEBUG(1, ("g_lock_init: Could not open g_lock.tdb"));
  		TALLOC_FREE(result);
  		return NULL;
  	}
  	return result;
  }
  
  static bool g_lock_conflicts(enum g_lock_type lock_type,
  			     const struct g_lock_rec *rec)
  {
  	enum g_lock_type rec_lock = rec->lock_type;
  
  	if ((rec_lock & G_LOCK_PENDING) != 0) {
  		return false;
  	}
  
  	/*
  	 * Only tested write locks so far. Very likely this routine
  	 * needs to be fixed for read locks....
  	 */
  	if ((lock_type == G_LOCK_READ) && (rec_lock == G_LOCK_READ)) {
  		return false;
  	}
  	return true;
  }
  
  static bool g_lock_parse(TALLOC_CTX *mem_ctx, TDB_DATA data,
  			 int *pnum_locks, struct g_lock_rec **plocks)
  {
  	int i, num_locks;
  	struct g_lock_rec *locks;
  
  	if ((data.dsize % sizeof(struct g_lock_rec)) != 0) {
  		DEBUG(1, ("invalid lock record length %d\n", (int)data.dsize));
  		return false;
  	}
  
  	num_locks = data.dsize / sizeof(struct g_lock_rec);
  	locks = talloc_array(mem_ctx, struct g_lock_rec, num_locks);
  	if (locks == NULL) {
  		DEBUG(1, ("talloc failed\n"));
  		return false;
  	}
  
  	memcpy(locks, data.dptr, data.dsize);
  
  	DEBUG(10, ("locks:\n"));
  	for (i=0; i<num_locks; i++) {
  		DEBUGADD(10, ("%s: %s %s\n",
  			      procid_str(talloc_tos(), &locks[i].pid),
  			      ((locks[i].lock_type & 1) == G_LOCK_READ) ?
  			      "read" : "write",
  			      (locks[i].lock_type & G_LOCK_PENDING) ?
  			      "(pending)" : "(owner)"));
  
  		if (((locks[i].lock_type & G_LOCK_PENDING) == 0)
  		    && !process_exists(locks[i].pid)) {
  
  			DEBUGADD(10, ("lock owner %s died -- discarding\n",
  				      procid_str(talloc_tos(),
  						 &locks[i].pid)));
  
  			if (i < (num_locks-1)) {
  				locks[i] = locks[num_locks-1];
  			}
  			num_locks -= 1;
  		}
  	}
  
  	*plocks = locks;
  	*pnum_locks = num_locks;
  	return true;
  }
  
  static void g_lock_cleanup(int *pnum_locks, struct g_lock_rec *locks)
  {
  	int i, num_locks;
  
  	num_locks = *pnum_locks;
  
  	DEBUG(10, ("g_lock_cleanup: %d locks\n", num_locks));
  
  	for (i=0; i<num_locks; i++) {
  		if (process_exists(locks[i].pid)) {
  			continue;
  		}
  		DEBUGADD(10, ("%s does not exist -- discarding\n",
  			      procid_str(talloc_tos(), &locks[i].pid)));
  
  		if (i < (num_locks-1)) {
  			locks[i] = locks[num_locks-1];
  		}
  		num_locks -= 1;
  	}
  	*pnum_locks = num_locks;
  	return;
  }
  
  static struct g_lock_rec *g_lock_addrec(TALLOC_CTX *mem_ctx,
  					struct g_lock_rec *locks,
  					int *pnum_locks,
  					const struct server_id pid,
  					enum g_lock_type lock_type)
  {
  	struct g_lock_rec *result;
  	int num_locks = *pnum_locks;
  
  	result = talloc_realloc(mem_ctx, locks, struct g_lock_rec,
  				num_locks+1);
  	if (result == NULL) {
  		return NULL;
  	}
  
  	result[num_locks].pid = pid;
  	result[num_locks].lock_type = lock_type;
  	*pnum_locks += 1;
  	return result;
  }
  
  static void g_lock_got_retry(struct messaging_context *msg,
  			     void *private_data,
  			     uint32_t msg_type,
  			     struct server_id server_id,
  			     DATA_BLOB *data);
  
  static NTSTATUS g_lock_trylock(struct g_lock_ctx *ctx, const char *name,
  			       enum g_lock_type lock_type)
  {
  	struct db_record *rec = NULL;
  	struct g_lock_rec *locks = NULL;
  	int i, num_locks;
  	struct server_id self;
  	int our_index;
  	TDB_DATA data;
  	NTSTATUS status = NT_STATUS_OK;
  	NTSTATUS store_status;
  
  again:
  	rec = ctx->db->fetch_locked(ctx->db, talloc_tos(),
  				    string_term_tdb_data(name));
  	if (rec == NULL) {
  		DEBUG(10, ("fetch_locked(\"%s\") failed\n", name));
  		status = NT_STATUS_LOCK_NOT_GRANTED;
  		goto done;
  	}
  
  	if (!g_lock_parse(talloc_tos(), rec->value, &num_locks, &locks)) {
  		DEBUG(10, ("g_lock_parse for %s failed\n", name));
  		status = NT_STATUS_INTERNAL_ERROR;
  		goto done;
  	}
  
  	self = procid_self();
  	our_index = -1;
  
  	for (i=0; i<num_locks; i++) {
  		if (procid_equal(&self, &locks[i].pid)) {
  			if (our_index != -1) {
  				DEBUG(1, ("g_lock_trylock: Added ourself "
  					  "twice!\n"));
  				status = NT_STATUS_INTERNAL_ERROR;
  				goto done;
  			}
  			if ((locks[i].lock_type & G_LOCK_PENDING) == 0) {
  				DEBUG(1, ("g_lock_trylock: Found ourself not "
  					  "pending!\n"));
  				status = NT_STATUS_INTERNAL_ERROR;
  				goto done;
  			}
  
  			our_index = i;
  
  			/* never conflict with ourself */
  			continue;
  		}
  		if (g_lock_conflicts(lock_type, &locks[i])) {
  			struct server_id pid = locks[i].pid;
  
  			if (!process_exists(pid)) {
  				TALLOC_FREE(locks);
  				TALLOC_FREE(rec);
  				status = g_lock_force_unlock(ctx, name, pid);
  				if (!NT_STATUS_IS_OK(status)) {
  					DEBUG(1, ("Could not unlock dead lock "
  						  "holder!\n"));
  					goto done;
  				}
  				goto again;
  			}
  			lock_type |= G_LOCK_PENDING;
  		}
  	}
  
  	if (our_index == -1) {
  		/* First round, add ourself */
  
  		locks = g_lock_addrec(talloc_tos(), locks, &num_locks,
  				      self, lock_type);
  		if (locks == NULL) {
  			DEBUG(10, ("g_lock_addrec failed\n"));
  			status = NT_STATUS_NO_MEMORY;
  			goto done;
  		}
  	} else {
  		/*
  		 * Retry. We were pending last time. Overwrite the
  		 * stored lock_type with what we calculated, we might
  		 * have acquired the lock this time.
  		 */
  		locks[our_index].lock_type = lock_type;
  	}
  
  	if (NT_STATUS_IS_OK(status) && ((lock_type & G_LOCK_PENDING) == 0)) {
  		/*
  		 * Walk through the list of locks, search for dead entries
  		 */
  		g_lock_cleanup(&num_locks, locks);
  	}
  
  	data = make_tdb_data((uint8_t *)locks, num_locks * sizeof(*locks));
  	store_status = rec->store(rec, data, 0);
  	if (!NT_STATUS_IS_OK(store_status)) {
  		DEBUG(1, ("rec->store failed: %s\n",
  			  nt_errstr(store_status)));
  		status = store_status;
  	}
  
  done:
  	TALLOC_FREE(locks);
  	TALLOC_FREE(rec);
  
  	if (NT_STATUS_IS_OK(status) && (lock_type & G_LOCK_PENDING) != 0) {
  		return STATUS_PENDING;
  	}
  
  	return NT_STATUS_OK;
  }
  
  NTSTATUS g_lock_lock(struct g_lock_ctx *ctx, const char *name,
  		     enum g_lock_type lock_type, struct timeval timeout)
  {
  	struct tevent_timer *te = NULL;
  	NTSTATUS status;
  	bool retry = false;
  	struct timeval timeout_end;
  	struct timeval time_now;
  
  	DEBUG(10, ("Trying to acquire lock %d for %s\n", (int)lock_type,
  		   name));
  
  	if (lock_type & ~1) {
  		DEBUG(1, ("Got invalid lock type %d for %s\n",
  			  (int)lock_type, name));
  		return NT_STATUS_INVALID_PARAMETER;
  	}
  
  #ifdef CLUSTER_SUPPORT
  	if (lp_clustering()) {
  		status = ctdb_watch_us(messaging_ctdbd_connection());
  		if (!NT_STATUS_IS_OK(status)) {
  			DEBUG(10, ("could not register retry with ctdb: %s\n",
  				   nt_errstr(status)));
  			goto done;
  		}
  	}
  #endif
  
  	status = messaging_register(ctx->msg, &retry, MSG_DBWRAP_G_LOCK_RETRY,
  				    g_lock_got_retry);
  	if (!NT_STATUS_IS_OK(status)) {
  		DEBUG(10, ("messaging_register failed: %s\n",
  			   nt_errstr(status)));
  		return status;
  	}
  
  	time_now = timeval_current();
  	timeout_end = timeval_sum(&time_now, &timeout);
  
  	while (true) {
  #ifdef CLUSTER_SUPPORT
  		fd_set _r_fds;
  #endif
  		fd_set *r_fds = NULL;
  		int max_fd = 0;
  		int ret;
  		struct timeval timeout_remaining, select_timeout;
  
  		status = g_lock_trylock(ctx, name, lock_type);
  		if (NT_STATUS_IS_OK(status)) {
  			DEBUG(10, ("Got lock %s\n", name));
  			break;
  		}
  		if (!NT_STATUS_EQUAL(status, STATUS_PENDING)) {
  			DEBUG(10, ("g_lock_trylock failed: %s\n",
  				   nt_errstr(status)));
  			break;
  		}
  
  		DEBUG(10, ("g_lock_trylock: Did not get lock, waiting...\n"));
  
  		/* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  		 *             !!! HACK ALERT --- FIX ME !!!
  		 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  		 * What we really want to do here is to react to
  		 * MSG_DBWRAP_G_LOCK_RETRY messages that are either sent
  		 * by a client doing g_lock_unlock or by ourselves when
  		 * we receive a CTDB_SRVID_SAMBA_NOTIFY or
  		 * CTDB_SRVID_RECONFIGURE message from ctdbd, i.e. when
  		 * either a client holding a lock or a complete node
  		 * has died.
  		 *
  		 * Doing this properly involves calling tevent_loop_once(),
  		 * but doing this here with the main ctdbd messaging context
  		 * creates a nested event loop when g_lock_lock() is called
  		 * from the main event loop, e.g. in a tcon_and_X where the
  		 * share_info.tdb needs to be initialized and is locked by
  		 * another process, or when the remore registry is accessed
  		 * for writing and some other process already holds a lock
  		 * on the registry.tdb.
  		 *
  		 * So as a quick fix, we act a little coarsely here: we do
  		 * a select on the ctdb connection fd and when it is readable
  		 * or we get EINTR, then we retry without actually parsing
  		 * any ctdb packages or dispatching messages. This means that
  		 * we retry more often than intended by design, but this does
  		 * not harm and it is unobtrusive. When we have finished,
  		 * the main loop will pick up all the messages and ctdb
  		 * packets. The only extra twist is that we cannot use timed
  		 * events here but have to handcode a timeout.
  		 */
  
  #ifdef CLUSTER_SUPPORT
  		if (lp_clustering()) {
  			struct ctdbd_connection *conn = messaging_ctdbd_connection();
  
  			r_fds = &_r_fds;
  			FD_ZERO(r_fds);
  			max_fd = ctdbd_conn_get_fd(conn);
  			if (max_fd >= 0 && max_fd < FD_SETSIZE) {
  				FD_SET(max_fd, r_fds);
  			}
  		}
  #endif
  
  		time_now = timeval_current();
  		timeout_remaining = timeval_until(&time_now, &timeout_end);
  		select_timeout = timeval_set(60, 0);
  
  		select_timeout = timeval_min(&select_timeout,
  					     &timeout_remaining);
  
  		ret = sys_select(max_fd + 1, r_fds, NULL, NULL,
  				 &select_timeout);
  		if (ret == -1) {
  			if (errno != EINTR) {
  				DEBUG(1, ("error calling select: %s\n",
  					  strerror(errno)));
  				status = NT_STATUS_INTERNAL_ERROR;
  				break;
  			}
  			/*
  			 * errno == EINTR:
  			 * This means a signal was received.
  			 * It might have been a MSG_DBWRAP_G_LOCK_RETRY message.
  			 * ==> retry
  			 */
  		} else if (ret == 0) {
  			if (timeval_expired(&timeout_end)) {
  				DEBUG(10, ("g_lock_lock timed out\n"));
  				status = NT_STATUS_LOCK_NOT_GRANTED;
  				break;
  			} else {
  				DEBUG(10, ("select returned 0 but timeout not "
  					   "not expired, retrying\n"));
  			}
  		} else if (ret != 1) {
  			DEBUG(1, ("invalid return code of select: %d\n", ret));
  			status = NT_STATUS_INTERNAL_ERROR;
  			break;
  		}
  		/*
  		 * ret == 1:
  		 * This means ctdbd has sent us some data.
  		 * Might be a CTDB_SRVID_RECONFIGURE or a
  		 * CTDB_SRVID_SAMBA_NOTIFY message.
  		 * ==> retry
  		 */
  	}
  
  #ifdef CLUSTER_SUPPORT
  done:
  #endif
  
  	if (!NT_STATUS_IS_OK(status)) {
  		NTSTATUS unlock_status;
  
  		unlock_status = g_lock_unlock(ctx, name);
  
  		if (!NT_STATUS_IS_OK(unlock_status)) {
  			DEBUG(1, ("Could not remove ourself from the locking "
  				  "db: %s\n", nt_errstr(status)));
  		}
  	}
  
  	messaging_deregister(ctx->msg, MSG_DBWRAP_G_LOCK_RETRY, &retry);
  	TALLOC_FREE(te);
  
  	return status;
  }
  
  static void g_lock_got_retry(struct messaging_context *msg,
  			     void *private_data,
  			     uint32_t msg_type,
  			     struct server_id server_id,
  			     DATA_BLOB *data)
  {
  	bool *pretry = (bool *)private_data;
  
  	DEBUG(10, ("Got retry message from pid %s\n",
  		   procid_str(talloc_tos(), &server_id)));
  
  	*pretry = true;
  }
  
  static NTSTATUS g_lock_force_unlock(struct g_lock_ctx *ctx, const char *name,
  				    struct server_id pid)
  {
  	struct db_record *rec = NULL;
  	struct g_lock_rec *locks = NULL;
  	int i, num_locks;
  	enum g_lock_type lock_type;
  	NTSTATUS status;
  
  	rec = ctx->db->fetch_locked(ctx->db, talloc_tos(),
  				    string_term_tdb_data(name));
  	if (rec == NULL) {
  		DEBUG(10, ("fetch_locked(\"%s\") failed\n", name));
  		status = NT_STATUS_INTERNAL_ERROR;
  		goto done;
  	}
  
  	if (!g_lock_parse(talloc_tos(), rec->value, &num_locks, &locks)) {
  		DEBUG(10, ("g_lock_parse for %s failed\n", name));
  		status = NT_STATUS_INTERNAL_ERROR;
  		goto done;
  	}
  
  	for (i=0; i<num_locks; i++) {
  		if (procid_equal(&pid, &locks[i].pid)) {
  			break;
  		}
  	}
  
  	if (i == num_locks) {
  		DEBUG(10, ("g_lock_force_unlock: Lock not found\n"));
  		status = NT_STATUS_INTERNAL_ERROR;
  		goto done;
  	}
  
  	lock_type = locks[i].lock_type;
  
  	if (i < (num_locks-1)) {
  		locks[i] = locks[num_locks-1];
  	}
  	num_locks -= 1;
  
  	if (num_locks == 0) {
  		status = rec->delete_rec(rec);
  	} else {
  		TDB_DATA data;
  		data = make_tdb_data((uint8_t *)locks,
  				     sizeof(struct g_lock_rec) * num_locks);
  		status = rec->store(rec, data, 0);
  	}
  
  	if (!NT_STATUS_IS_OK(status)) {
  		DEBUG(1, ("g_lock_force_unlock: Could not store record: %s\n",
  			  nt_errstr(status)));
  		goto done;
  	}
  
  	TALLOC_FREE(rec);
  
  	if ((lock_type & G_LOCK_PENDING) == 0) {
  		int num_wakeups = 0;
  
  		/*
  		 * We've been the lock holder. Others to retry. Don't
  		 * tell all others to avoid a thundering herd. In case
  		 * this leads to a complete stall because we miss some
  		 * processes, the loop in g_lock_lock tries at least
  		 * once a minute.
  		 */
  
  		for (i=0; i<num_locks; i++) {
  			if ((locks[i].lock_type & G_LOCK_PENDING) == 0) {
  				continue;
  			}
  			if (!process_exists(locks[i].pid)) {
  				continue;
  			}
  
  			/*
  			 * Ping all waiters to retry
  			 */
  			status = messaging_send(ctx->msg, locks[i].pid,
  						MSG_DBWRAP_G_LOCK_RETRY,
  						&data_blob_null);
  			if (!NT_STATUS_IS_OK(status)) {
  				DEBUG(1, ("sending retry to %s failed: %s\n",
  					  procid_str(talloc_tos(),
  						     &locks[i].pid),
  					  nt_errstr(status)));
  			} else {
  				num_wakeups += 1;
  			}
  			if (num_wakeups > 5) {
  				break;
  			}
  		}
  	}
  done:
  	/*
  	 * For the error path, TALLOC_FREE(rec) as well. In the good
  	 * path we have already freed it.
  	 */
  	TALLOC_FREE(rec);
  
  	TALLOC_FREE(locks);
  	return status;
  }
  
  NTSTATUS g_lock_unlock(struct g_lock_ctx *ctx, const char *name)
  {
  	NTSTATUS status;
  
  	status = g_lock_force_unlock(ctx, name, procid_self());
  
  #ifdef CLUSTER_SUPPORT
  	if (lp_clustering()) {
  		ctdb_unwatch(messaging_ctdbd_connection());
  	}
  #endif
  	return status;
  }
  
  struct g_lock_locks_state {
  	int (*fn)(const char *name, void *private_data);
  	void *private_data;
  };
  
  static int g_lock_locks_fn(struct db_record *rec, void *priv)
  {
  	struct g_lock_locks_state *state = (struct g_lock_locks_state *)priv;
  
  	if ((rec->key.dsize == 0) || (rec->key.dptr[rec->key.dsize-1] != 0)) {
  		DEBUG(1, ("invalid key in g_lock.tdb, ignoring\n"));
  		return 0;
  	}
  	return state->fn((char *)rec->key.dptr, state->private_data);
  }
  
  int g_lock_locks(struct g_lock_ctx *ctx,
  		 int (*fn)(const char *name, void *private_data),
  		 void *private_data)
  {
  	struct g_lock_locks_state state;
  
  	state.fn = fn;
  	state.private_data = private_data;
  
  	return ctx->db->traverse_read(ctx->db, g_lock_locks_fn, &state);
  }
  
  NTSTATUS g_lock_dump(struct g_lock_ctx *ctx, const char *name,
  		     int (*fn)(struct server_id pid,
  			       enum g_lock_type lock_type,
  			       void *private_data),
  		     void *private_data)
  {
  	TDB_DATA data;
  	int i, num_locks;
  	struct g_lock_rec *locks = NULL;
  	bool ret;
  
  	if (ctx->db->fetch(ctx->db, talloc_tos(), string_term_tdb_data(name),
  			   &data) != 0) {
  		return NT_STATUS_NOT_FOUND;
  	}
  
  	if ((data.dsize == 0) || (data.dptr == NULL)) {
  		return NT_STATUS_OK;
  	}
  
  	ret = g_lock_parse(talloc_tos(), data, &num_locks, &locks);
  
  	TALLOC_FREE(data.dptr);
  
  	if (!ret) {
  		DEBUG(10, ("g_lock_parse for %s failed\n", name));
  		return NT_STATUS_INTERNAL_ERROR;
  	}
  
  	for (i=0; i<num_locks; i++) {
  		if (fn(locks[i].pid, locks[i].lock_type, private_data) != 0) {
  			break;
  		}
  	}
  	TALLOC_FREE(locks);
  	return NT_STATUS_OK;
  }
  
  struct g_lock_get_state {
  	bool found;
  	struct server_id *pid;
  };
  
  static int g_lock_get_fn(struct server_id pid, enum g_lock_type lock_type,
  			 void *priv)
  {
  	struct g_lock_get_state *state = (struct g_lock_get_state *)priv;
  
  	if ((lock_type & G_LOCK_PENDING) != 0) {
  		return 0;
  	}
  
  	state->found = true;
  	*state->pid = pid;
  	return 1;
  }
  
  NTSTATUS g_lock_get(struct g_lock_ctx *ctx, const char *name,
  		    struct server_id *pid)
  {
  	struct g_lock_get_state state;
  	NTSTATUS status;
  
  	state.found = false;
  	state.pid = pid;
  
  	status = g_lock_dump(ctx, name, g_lock_get_fn, &state);
  	if (!NT_STATUS_IS_OK(status)) {
  		return status;
  	}
  	if (!state.found) {
  		return NT_STATUS_NOT_FOUND;
  	}
  	return NT_STATUS_OK;
  }
  
  static bool g_lock_init_all(TALLOC_CTX *mem_ctx,
  			    struct tevent_context **pev,
  			    struct messaging_context **pmsg,
  			    struct g_lock_ctx **pg_ctx)
  {
  	struct tevent_context *ev = NULL;
  	struct messaging_context *msg = NULL;
  	struct g_lock_ctx *g_ctx = NULL;
  
  	ev = tevent_context_init(mem_ctx);
  	if (ev == NULL) {
  		d_fprintf(stderr, "ERROR: could not init event context\n");
  		goto fail;
  	}
  	msg = messaging_init(mem_ctx, procid_self(), ev);
  	if (msg == NULL) {
  		d_fprintf(stderr, "ERROR: could not init messaging context\n");
  		goto fail;
  	}
  	g_ctx = g_lock_ctx_init(mem_ctx, msg);
  	if (g_ctx == NULL) {
  		d_fprintf(stderr, "ERROR: could not init g_lock context\n");
  		goto fail;
  	}
  
  	*pev = ev;
  	*pmsg = msg;
  	*pg_ctx = g_ctx;
  	return true;
  fail:
  	TALLOC_FREE(g_ctx);
  	TALLOC_FREE(msg);
  	TALLOC_FREE(ev);
  	return false;
  }
  
  NTSTATUS g_lock_do(const char *name, enum g_lock_type lock_type,
  		   struct timeval timeout,
  		   void (*fn)(void *private_data), void *private_data)
  {
  	struct tevent_context *ev = NULL;
  	struct messaging_context *msg = NULL;
  	struct g_lock_ctx *g_ctx = NULL;
  	NTSTATUS status;
  
  	if (!g_lock_init_all(talloc_tos(), &ev, &msg, &g_ctx)) {
  		status = NT_STATUS_ACCESS_DENIED;
  		goto done;
  	}
  
  	status = g_lock_lock(g_ctx, name, lock_type, timeout);
  	if (!NT_STATUS_IS_OK(status)) {
  		goto done;
  	}
  	fn(private_data);
  	g_lock_unlock(g_ctx, name);
  
  done:
  	TALLOC_FREE(g_ctx);
  	TALLOC_FREE(msg);
  	TALLOC_FREE(ev);
  	return status;
  }
  