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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
Download Patch File Download Diff File Expand all files Collapse all files

55
lib/commands/toolcontext.c
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@@ -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;
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;
/*
* 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"))) {