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udev: recognize DM_DISABLE_UDEV environment variable

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Setting this environment variable will cause a full fallback
to old direct node and symlink management in libdevmapper and lvm2.

It means:

 - disabling udev synchronization
   (--noudevsync in dmsetup and --noudevsync + activation/udev_sync=0
    lvm2 config)
 - disabling dm and any subsystem related udev rules
   (--noudevrules in dmsetup and activation/udev_rules=0 lvm2 config)
 - management of nodes/symlinks under /dev directly by libdevmapper/lvm2
   (--verifyudev in dmsetup and activation/verify_udev_operations=1
    lvm2 config)
 - not obtaining any device list from udev database
   (devices/obtain_device_list_from_udev=0 lvm2 config)

Note: we could set all of these before - there's no functional change!
However the DM_DISABLE_UDEV environment variable is a nice shortcut
to make it easier for libdevmapper users so that one can switch off all
of the udev management off at one go directly on the command line,
without a need to modify any source or add any extra switches.
This commit is contained in:
Peter Rajnoha 2012-11-29 14:03:48 +01:00
parent fb8cc7c63f
commit 4891a735d3
4 changed files with 71 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
WHATS_NEW
View File

@ -1,5 +1,6 @@
Version 2.02.99 -
===================================
Recognize DM_DISABLE_UDEV environment variable for a complete fallback.
Do not verify udev operations if --noudevsync command option is used.
Fix lvm2api and return lvseg discards property as string.
Allow forced vgcfgrestore of lvm2 metadata with thin volumes.

1
WHATS_NEW_DM
View File

@ -1,5 +1,6 @@
Version 1.02.78 -
===================================
Add DM_DISABLE_UDEV environment variable to manage dev nodes by libdm only.
Fix dm_task_set_cookie to properly process udev flags if udev_sync disabled.
Version 1.02.77 - 15th October 2012

49
lib/commands/toolcontext.c
View File

@ -237,6 +237,7 @@ static int _process_config(struct cmd_context *cmd)
const struct dm_config_value *cv;
int64_t pv_min_kb;
const char *lvmetad_socket;
int udev_disabled = 0;
/* umask */
cmd->default_settings.umask = find_config_tree_int(cmd,
@ -310,13 +311,25 @@ static int _process_config(struct cmd_context *cmd)
return 0;
}
cmd->default_settings.udev_rules = find_config_tree_int(cmd,
"activation/udev_rules",
DEFAULT_UDEV_RULES);
/*
* If udev is disabled using DM_DISABLE_UDEV environment
* variable, override existing config and hardcode these:
* - udev_rules = 0
* - udev_sync = 0
* - udev_fallback = 1
*/
if (getenv("DM_DISABLE_UDEV")) {
log_very_verbose("DM_DISABLE_UDEV environment variable set. "
"Overriding configuration to use "
"udev_rules=0, udev_sync=0, verify_udev_operations=1.");
udev_disabled = 1;
}
cmd->default_settings.udev_sync = find_config_tree_int(cmd,
"activation/udev_sync",
DEFAULT_UDEV_SYNC);
cmd->default_settings.udev_rules = udev_disabled ? 0 :
find_config_tree_int(cmd, "activation/udev_rules", DEFAULT_UDEV_RULES);
cmd->default_settings.udev_sync = udev_disabled ? 0 :
find_config_tree_int(cmd, "activation/udev_sync", DEFAULT_UDEV_SYNC);
init_retry_deactivation(find_config_tree_int(cmd, "activation/retry_deactivation",
DEFAULT_RETRY_DEACTIVATION));
@ -326,14 +339,12 @@ static int _process_config(struct cmd_context *cmd)
#ifdef UDEV_SYNC_SUPPORT
/*
* We need udev rules to be applied, otherwise we would end up with no
* nodes and symlinks! However, we can disable the synchronization itself
* in runtime and still have only udev to create the nodes and symlinks
* without any fallback.
* Use udev fallback automatically in case udev
* is disabled via DM_DISABLE_UDEV environment
* variable or udev rules are switched off.
*/
cmd->default_settings.udev_fallback = cmd->default_settings.udev_rules ?
find_config_tree_int(cmd, "activation/verify_udev_operations",
DEFAULT_VERIFY_UDEV_OPERATIONS) : 1;
cmd->default_settings.udev_fallback = !cmd->default_settings.udev_rules || udev_disabled ? 1 :
find_config_tree_int(cmd, "activation/verify_udev_operations", DEFAULT_VERIFY_UDEV_OPERATIONS);
/* Do not rely fully on udev if the udev support is known to be incomplete. */
if (!cmd->default_settings.udev_fallback && !_dm_driver_has_stable_udev_support()) {
@ -693,9 +704,21 @@ static int _init_dev_cache(struct cmd_context *cmd)
if (!dev_cache_init(cmd))
return_0;
/*
* Override existing config and hardcode device_list_from_udev = 0 if:
* - udev is not running
* - udev is disabled using DM_DISABLE_UDEV environment variable
*/
if (getenv("DM_DISABLE_UDEV")) {
log_very_verbose("DM_DISABLE_UDEV environment variable set. "
"Overriding configuration to use "
"device_list_from_udev=0");
device_list_from_udev = 0;
} else
device_list_from_udev = udev_is_running() ?
find_config_tree_bool(cmd, "devices/obtain_device_list_from_udev",
DEFAULT_OBTAIN_DEVICE_LIST_FROM_UDEV) : 0;
init_obtain_device_list_from_udev(device_list_from_udev);
if (!(cn = find_config_tree_node(cmd, "devices/scan"))) {

34
libdm/libdm-common.c
View File

@ -75,6 +75,7 @@ static struct selabel_handle *_selabel_handle = NULL;
#endif
#ifdef UDEV_SYNC_SUPPORT
static int _udev_disabled = 0;
static int _semaphore_supported = -1;
static int _udev_running = -1;
static int _sync_with_udev = 1;
@ -85,6 +86,9 @@ void dm_lib_init(void)
{
const char *env;
if ((env = getenv("DM_DISABLE_UDEV")))
_udev_disabled = 1;
env = getenv(DM_DEFAULT_NAME_MANGLING_MODE_ENV_VAR_NAME);
if (env && *env) {
if (!strcasecmp(env, "none"))
@ -1814,6 +1818,26 @@ out:
return r;
}
static void _set_cookie_flags(struct dm_task *dmt, uint16_t flags)
{
if (!dm_cookie_supported())
return;
if (_udev_disabled) {
/*
* If udev is disabled, hardcode this functionality:
* - we want libdm to create the nodes
* - we don't want the /dev/mapper and any subsystem
* related content to be created by udev if udev
* rules are installed
*/
flags &= ~DM_UDEV_DISABLE_LIBRARY_FALLBACK;
flags |= DM_UDEV_DISABLE_DM_RULES_FLAG | DM_UDEV_DISABLE_SUBSYSTEM_RULES_FLAG;
}
dmt->event_nr = flags << DM_UDEV_FLAGS_SHIFT;
}
#ifndef UDEV_SYNC_SUPPORT
void dm_udev_set_sync_support(int sync_with_udev)
{
@ -1835,8 +1859,8 @@ int dm_udev_get_checking(void)
int dm_task_set_cookie(struct dm_task *dmt, uint32_t *cookie, uint16_t flags)
{
if (dm_cookie_supported())
dmt->event_nr = flags << DM_UDEV_FLAGS_SHIFT;
_set_cookie_flags(dmt, flags);
*cookie = 0;
dmt->cookie_set = 1;
@ -1920,6 +1944,9 @@ void dm_udev_set_sync_support(int sync_with_udev)
int dm_udev_get_sync_support(void)
{
if (_udev_disabled)
return 0;
_check_udev_sync_requirements_once();
return _semaphore_supported && dm_cookie_supported() &&
@ -2203,8 +2230,7 @@ int dm_task_set_cookie(struct dm_task *dmt, uint32_t *cookie, uint16_t flags)
{
int semid;
if (dm_cookie_supported())
dmt->event_nr = flags << DM_UDEV_FLAGS_SHIFT;
_set_cookie_flags(dmt, flags);
if (!dm_udev_get_sync_support()) {
*cookie = 0;