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toolcontext: check dm version lazily for udev_fallback setting

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Setting the cmd->default_settings.udev_fallback also requires DM
driver version check. However, this caused useless mapper/control
access with ioctl if not needed actually. For example if we're not
using activation code, we don't need to know the udev_fallback as
there's no node and symlink processing.

For example, this premature mapper/control access caused problems
when using lvm2app even when no activation happens - there are
situations in which we don't need to use mapper/control, but still
need some of the lvm2app functionality. This is also the case for
lvm2-activation systemd generator which just needs to look at the
lvm2 configuration, but it shouldn't touch mapper/control.
This commit is contained in:
Peter Rajnoha 2013-05-13 11:46:24 +02:00
parent 3d0cb0611e
commit 4407133113
3 changed files with 63 additions and 41 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 -
===================================
Fix premature DM version checking which caused useless mapper/control access.
Add "active" LV reporting field to show activation state.
Add "monitor" segment reporting field to show dmevent monitoring status.
Document lvextend --use-policies option in man.

57
lib/activate/dev_manager.c
View File

@ -1309,6 +1309,57 @@ int dev_manager_mknodes(const struct logical_volume *lv)
return r;
}
#ifdef UDEV_SYNC_SUPPORT
/*
* Until the DM_UEVENT_GENERATED_FLAG was introduced in kernel patch
* 856a6f1dbd8940e72755af145ebcd806408ecedd
* some operations could not be performed by udev, requiring our fallback code.
*/
static int _dm_driver_has_stable_udev_support(void)
{
char vsn[80];
unsigned maj, min, patchlevel;
return driver_version(vsn, sizeof(vsn)) &&
(sscanf(vsn, "%u.%u.%u", &maj, &min, &patchlevel) == 3) &&
(maj == 4 ? min >= 18 : maj > 4);
}
static int _check_udev_fallback(struct cmd_context *cmd)
{
struct config_info *settings = &cmd->current_settings;
if (settings->udev_fallback != -1)
goto out;
/*
* Use udev fallback automatically in case udev
* is disabled via DM_DISABLE_UDEV environment
* variable or udev rules are switched off.
*/
settings->udev_fallback = !settings->udev_rules ? 1 :
find_config_tree_bool(cmd, activation_verify_udev_operations_CFG);
/* Do not rely fully on udev if the udev support is known to be incomplete. */
if (!settings->udev_fallback && !_dm_driver_has_stable_udev_support()) {
log_very_verbose("Kernel driver has incomplete udev support so "
"LVM will check and perform some operations itself.");
settings->udev_fallback = 1;
}
out:
return settings->udev_fallback;
}
#else /* UDEV_SYNC_SUPPORT */
static int _check_udev_fallback(struct cmd_context *cmd)
{
/* We must use old node/symlink creation code if not compiled with udev support at all! */
return cmd->current_settings.udev_fallback = 1;
}
#endif /* UDEV_SYNC_SUPPORT */
static uint16_t _get_udev_flags(struct dev_manager *dm, struct logical_volume *lv,
const char *layer)
{
@ -1318,7 +1369,7 @@ static uint16_t _get_udev_flags(struct dev_manager *dm, struct logical_volume *l
* Instruct also libdevmapper to disable udev
* fallback in accordance to LVM2 settings.
*/
if (!dm->cmd->current_settings.udev_fallback)
if (!_check_udev_fallback(dm->cmd))
udev_flags |= DM_UDEV_DISABLE_LIBRARY_FALLBACK;
/*
@ -2399,7 +2450,7 @@ static int _create_lv_symlinks(struct dev_manager *dm, struct dm_tree_node *root
int r = 1;
/* Nothing to do if udev fallback is disabled. */
if (!dm->cmd->current_settings.udev_fallback) {
if (!_check_udev_fallback(dm->cmd)) {
fs_set_create();
return 1;
}
@ -2447,7 +2498,7 @@ static int _remove_lv_symlinks(struct dev_manager *dm, struct dm_tree_node *root
int r = 1;
/* Nothing to do if udev fallback is disabled. */
if (!dm->cmd->current_settings.udev_fallback)
if (!_check_udev_fallback(dm->cmd))
return 1;
while ((child = dm_tree_next_child(&handle, root, 0))) {

46
lib/commands/toolcontext.c
View File

@ -262,23 +262,6 @@ static int _check_disable_udev(const char *msg) {
return 0;
}
#ifdef UDEV_SYNC_SUPPORT
/*
* Until the DM_UEVENT_GENERATED_FLAG was introduced in kernel patch
* 856a6f1dbd8940e72755af145ebcd806408ecedd
* some operations could not be performed by udev, requiring our fallback code.
*/
static int _dm_driver_has_stable_udev_support(void)
{
char vsn[80];
unsigned maj, min, patchlevel;
return driver_version(vsn, sizeof(vsn)) &&
(sscanf(vsn, "%u.%u.%u", &maj, &min, &patchlevel) == 3) &&
(maj == 4 ? min >= 18 : maj > 4);
}
#endif
static int _process_config(struct cmd_context *cmd)
{
mode_t old_umask;
@ -372,31 +355,18 @@ static int _process_config(struct cmd_context *cmd)
cmd->default_settings.udev_sync = udev_disabled ? 0 :
find_config_tree_bool(cmd, activation_udev_sync_CFG);
/*
* Set udev_fallback lazily on first use since it requires
* checking DM driver version which is an extra ioctl!
* This also prevents unnecessary use of mapper/control.
* If udev is disabled globally, set fallback mode immediately.
*/
cmd->default_settings.udev_fallback = udev_disabled ? 1 : -1;
init_retry_deactivation(find_config_tree_bool(cmd, activation_retry_deactivation_CFG));
init_activation_checks(find_config_tree_bool(cmd, activation_checks_CFG));
#ifdef UDEV_SYNC_SUPPORT
/*
* 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 || udev_disabled ? 1 :
find_config_tree_bool(cmd, activation_verify_udev_operations_CFG);
/* 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()) {
log_very_verbose("Kernel driver has incomplete udev support so "
"LVM will check and perform some operations itself.");
cmd->default_settings.udev_fallback = 1;
}
#else
/* We must use old node/symlink creation code if not compiled with udev support at all! */
cmd->default_settings.udev_fallback = 1;
#endif
cmd->use_linear_target = find_config_tree_bool(cmd, activation_use_linear_target_CFG);
cmd->stripe_filler = find_config_tree_str(cmd, activation_missing_stripe_filler_CFG);