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lvm2/lib/locking/external_locking.c
Alasdair Kergon 25b733809a Merge with text format branch.
Lots of changes/very little testing so far => there'll be bugs!

Use 'vgcreate -M text' to create a volume group with its metadata stored
in text files.  Text format metadata changes should be reasonably atomic,
with a (basic) automatic recovery mechanism if the system crashes while a
change is in progress.

Add a metadata section to lvm.conf to specify multiple directories if
you want (recommended) to keep multiple copies of the metadata (eg on
different filesystems).

e.g. metadata {
        dirs = ["/etc/lvm/metadata1","/usr/local/lvm/metadata2"]
}

Plenty of refinements still in the pipeline.
2002-04-24 18:20:51 +00:00

116 lines
2.8 KiB
C

/*
* Copyright (C) 2002 Sistina Software (UK) Limited.
*
* This file is released under the LGPL.
*
*/
#include "log.h"
#include "locking.h"
#include "locking_types.h"
#include "activate.h"
#include "config.h"
#include "defaults.h"
#include "lvm-file.h"
#include "lvm-string.h"
#include "dbg_malloc.h"
#include <limits.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/file.h>
#include <fcntl.h>
#include <dlfcn.h>
#include <signal.h>
static void *locking_module = NULL;
static void (*end_fn) (void) = NULL;
static int (*lock_fn) (struct cmd_context * cmd, const char *resource,
int flags) = NULL;
static int (*init_fn) (int type, struct config_file * cf) = NULL;
static int lock_resource(struct cmd_context *cmd, const char *resource,
int flags)
{
if (lock_fn)
return lock_fn(cmd, resource, flags);
else
return 0;
}
static void fin_external_locking(void)
{
if (end_fn)
end_fn();
dlclose(locking_module);
locking_module = NULL;
end_fn = NULL;
lock_fn = NULL;
}
int init_external_locking(struct locking_type *locking, struct config_file *cf)
{
char _lock_lib[PATH_MAX];
if (locking_module) {
log_error("External locking already initialised");
return 1;
}
locking->lock_resource = lock_resource;
locking->fin_locking = fin_external_locking;
/* Get locking module name from config file */
strncpy(_lock_lib, find_config_str(cf->root, "global/locking_library",
'/', "lvm2_locking.so"),
sizeof(_lock_lib));
/* If there is a module_dir in the config file then
look for the locking module in there first and then
using the normal dlopen(3) mechanism of looking
down LD_LIBRARY_PATH and /lib, /usr/lib.
If course, if the library name starts with a slash then
just use the name... */
if (_lock_lib[0] != '/') {
struct stat st;
char _lock_lib1[PATH_MAX];
lvm_snprintf(_lock_lib1, sizeof(_lock_lib1),
"%s/%s",
find_config_str(cf->root, "global/module_dir",
'/', "RUBBISH"), _lock_lib);
/* Does it exist ? */
if (stat(_lock_lib1, &st) == 0) {
strcpy(_lock_lib, _lock_lib1);
}
}
log_very_verbose("Opening locking library %s", _lock_lib);
locking_module = dlopen(_lock_lib, RTLD_LAZY);
if (!locking_module) {
log_error("Unable to open external locking module %s",
_lock_lib);
return 0;
}
/* Get the functions we need */
init_fn = dlsym(locking_module, "init_locking");
lock_fn = dlsym(locking_module, "lock_resource");
end_fn = dlsym(locking_module, "end_locking");
/* Are they all there ? */
if (!end_fn || !init_fn || !lock_fn) {
log_error ("Shared library %s does not contain locking "
"functions", _lock_lib);
dlclose(locking_module);
return 0;
}
log_verbose("Opened external locking module %s", _lock_lib);
return init_fn(2, cf);
}