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      1 /*	$NetBSD: external_locking.c,v 1.1.1.2 2009/12/02 00:26:24 haad Exp $	*/
      2 
      3 /*
      4  * Copyright (C) 2002-2004 Sistina Software, Inc. All rights reserved.
      5  * Copyright (C) 2004-2006 Red Hat, Inc. All rights reserved.
      6  *
      7  * This file is part of LVM2.
      8  *
      9  * This copyrighted material is made available to anyone wishing to use,
     10  * modify, copy, or redistribute it subject to the terms and conditions
     11  * of the GNU Lesser General Public License v.2.1.
     12  *
     13  * You should have received a copy of the GNU Lesser General Public License
     14  * along with this program; if not, write to the Free Software Foundation,
     15  * Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
     16  */
     17 
     18 #include "lib.h"
     19 #include "locking_types.h"
     20 #include "defaults.h"
     21 #include "sharedlib.h"
     22 #include "toolcontext.h"
     23 
     24 static void *_locking_lib = NULL;
     25 static void (*_reset_fn) (void) = NULL;
     26 static void (*_end_fn) (void) = NULL;
     27 static int (*_lock_fn) (struct cmd_context * cmd, const char *resource,
     28 			uint32_t flags) = NULL;
     29 static int (*_init_fn) (int type, struct config_tree * cft,
     30 			uint32_t *flags) = NULL;
     31 static int (*_lock_query_fn) (const char *resource, int *mode) = NULL;
     32 
     33 static int _lock_resource(struct cmd_context *cmd, const char *resource,
     34 			  uint32_t flags)
     35 {
     36 	if (_lock_fn)
     37 		return _lock_fn(cmd, resource, flags);
     38 	else
     39 		return 0;
     40 }
     41 
     42 static void _fin_external_locking(void)
     43 {
     44 	if (_end_fn)
     45 		_end_fn();
     46 
     47 	dlclose(_locking_lib);
     48 
     49 	_locking_lib = NULL;
     50 	_init_fn = NULL;
     51 	_end_fn = NULL;
     52 	_lock_fn = NULL;
     53 	_reset_fn = NULL;
     54 }
     55 
     56 static void _reset_external_locking(void)
     57 {
     58 	if (_reset_fn)
     59 		_reset_fn();
     60 }
     61 
     62 int init_external_locking(struct locking_type *locking, struct cmd_context *cmd)
     63 {
     64 	const char *libname;
     65 
     66 	if (_locking_lib) {
     67 		log_error("External locking already initialised");
     68 		return 1;
     69 	}
     70 
     71 	locking->lock_resource = _lock_resource;
     72 	locking->fin_locking = _fin_external_locking;
     73 	locking->reset_locking = _reset_external_locking;
     74 	locking->flags = 0;
     75 
     76 	libname = find_config_tree_str(cmd, "global/locking_library",
     77 				       DEFAULT_LOCKING_LIB);
     78 
     79 	if (!(_locking_lib = load_shared_library(cmd, libname, "locking", 1)))
     80 		return_0;
     81 
     82 	/* Get the functions we need */
     83 	if (!(_init_fn = dlsym(_locking_lib, "locking_init")) ||
     84 	    !(_lock_fn = dlsym(_locking_lib, "lock_resource")) ||
     85 	    !(_reset_fn = dlsym(_locking_lib, "reset_locking")) ||
     86 	    !(_end_fn = dlsym(_locking_lib, "locking_end"))) {
     87 		log_error("Shared library %s does not contain locking "
     88 			  "functions", libname);
     89 		dlclose(_locking_lib);
     90 		_locking_lib = NULL;
     91 		return 0;
     92 	}
     93 
     94 	if (!(_lock_query_fn = dlsym(_locking_lib, "query_resource")))
     95 		log_warn("WARNING: %s: _query_resource() missing: "
     96 			 "Using inferior activation method.", libname);
     97 
     98 	log_verbose("Loaded external locking library %s", libname);
     99 	return _init_fn(2, cmd->cft, &locking->flags);
    100 }
    101