static int _control_device_number(uint32_t *major, uint32_t *minor)
{
if (!_get_proc_number(PROC_DEVICES, MISC_NAME, major) ||
!_get_proc_number(PROC_MISC, DM_NAME, minor)) {
*major = 0;
return 0;
}
return 1;
}
/*
* FIXME Update bitset in long-running process if dm claims new major numbers.
*/
static int _create_dm_bitset(void)
{
#ifdef DM_IOCTLS
struct utsname uts;
if (_dm_bitset || _dm_device_major)
return 1;
if (uname(&uts))
return 0;
/*
* 2.6 kernels are limited to one major number.
* Assume 2.4 kernels are patched not to.
* FIXME Check _dm_version and _dm_version_minor if 2.6 changes this.
*/
if (!strncmp(uts.release, "2.6.", 4))
_dm_multiple_major_support = 0;
if (!_dm_multiple_major_support) {
if (!_get_proc_number(PROC_DEVICES, DM_NAME, &_dm_device_major))
return 0;
return 1;
}
/* Multiple major numbers supported */
if (!(_dm_bitset = dm_bitset_create(NULL, NUMBER_OF_MAJORS)))
return 0;
if (!_get_proc_number(PROC_DEVICES, DM_NAME, NULL)) {
dm_bitset_destroy(_dm_bitset);
_dm_bitset = NULL;
return 0;
}
return 1;
#else
return 0;
#endif
}
static int _open_control(void)
{
#ifdef DM_IOCTLS
char control[PATH_MAX];
uint32_t major = 0, minor;
int dm_mod_autoload_support, needs_open;
if (_control_fd != -1)
return 1;
if (!_uname())
return 0;
snprintf(control, sizeof(control), "%s/%s", dm_dir(), DM_CONTROL_NODE);
/*
* dm-mod autoloading is supported since kernel 2.6.36.
* Udev daemon will try to read modules.devname file extracted
* by depmod and create any static nodes needed.
* The /dev/mapper/control node can be created and prepared this way.
* First access to such node should load dm-mod module automatically.
*/
dm_mod_autoload_support = KERNEL_VERSION(_kernel_major, _kernel_minor,
_kernel_release) >= KERNEL_VERSION(2, 6, 36);
/*
* If dm-mod autoloading is supported and the control node exists
* already try to open it now. This should autoload dm-mod module.
*/
if (dm_mod_autoload_support) {
if (!_get_proc_number(PROC_DEVICES, MISC_NAME, &major))
/* If major not found, just fallback to hardcoded value. */
major = MISC_MAJOR;
/* Recreate the node with correct major and minor if needed. */
if (!_control_exists(control, major, MAPPER_CTRL_MINOR) &&
!_create_control(control, major, MAPPER_CTRL_MINOR))
goto error;
_open_and_assign_control_fd(control, 1);
}
/*
* Get major and minor number assigned for the control node.
* In case we make use of the module autoload support, this
* information should be accessible now as well.
*/
if (!_control_device_number(&major, &minor))
log_error("Is device-mapper driver missing from kernel?");
/*
* Check the control node and its major and minor number.
* If there's anything wrong, remove the old node and create
* a correct one.
*/
if ((needs_open = !_control_exists(control, major, minor)) &&
!_create_control(control, major, minor)) {
_close_control_fd();
goto error;
}
/*
* For older kernels without dm-mod autoloading support, we always
* need to open the control node here - we still haven't done that!
* For newer kernels with dm-mod autoloading, we open it only if the
* node was recreated and corrected in previous step.
*/
if ((!dm_mod_autoload_support || needs_open) &&
!_open_and_assign_control_fd(control, 0))
goto error;
if (!_create_dm_bitset()) {
log_error("Failed to set up list of device-mapper major numbers");
return 0;
}
return 1;
error:
log_error("Failure to communicate with kernel device-mapper driver.");
return 0;
#else
return 1;
#endif
}
