devices: rework libudev usage

related to config settings:
  obtain_device_info_from_udev (controls if lvm gets
    a list of devices from readdir /dev or from libudev)
  external_device_info_source (controls if lvm asks
    libudev for device information)

. Make the obtain_device_list_from_udev setting
  affect only the choice of readdir /dev vs libudev.
  The setting no longer controls if udev is used for
  device type checks.

. Change obtain_device_list_from_udev default to 0.
  This helps avoid boot timeouts due to slow libudev
  queries, avoids reported failures from
  udev_enumerate_scan_devices, and avoids delays from
  "device not initialized in udev database" errors.
  Even without errors, for a system booting with 1024 PVs,
  lvm2-pvscan times improve from about 100 sec to 15 sec,
  and the pvscan command from about 64 sec to about 4 sec.

. For external_device_info_source="none", remove all
  libudev device info queries, and use only lvm
  native device info.

. For external_device_info_source="udev", first check
  lvm native device info, then check libudev info.

. Remove sleep/retry loop when attempting libudev
  queries for device info.  udev info will simply
  be skipped if it's not immediately available.

. Only set up a libdev connection if it will be used by
  obtain_device_list_from_udev/external_device_info_source.

. For native multipath component detection, use
  /etc/multipath/wwids.  If a device has a wwid
  matching an entry in the wwids file, then it's
  considered a multipath component.  This is
  necessary to natively detect multipath
  components when the mpath device is not set up.

1 files changed, 1 insertions, 11 deletions

diff --git a/tools/pvscan.c b/tools/pvscan.c
index 464501ad5..40a93957c 100644
--- a/tools/pvscan.c
+++ b/tools/pvscan.c
@@ -1193,16 +1193,6 @@ static int _online_devs(struct cmd_context *cmd, int do_all, struct dm_list *pvs
 
 		log_debug("online_devs %s %s", dev_name(dev), dev->pvid);
 
-		/*
-		 * This should already have been done by the filter, but make
-		 * another check directly with udev in case the filter was not
-		 * using udev and the native version didn't catch it.
-		 */
-		if (udev_dev_is_mpath_component(dev)) {
-			log_print("pvscan[%d] ignore multipath component %s.", getpid(), dev_name(dev));
-			continue;
-		}
-
 		if (!(info = lvmcache_info_from_pvid(dev->pvid, dev, 0))) {
 			if (!do_all)
 				log_print("pvscan[%d] ignore %s with no lvm info.", getpid(), dev_name(dev));
@@ -1257,7 +1247,7 @@ static int _online_devs(struct cmd_context *cmd, int do_all, struct dm_list *pvs
 			if (pv->device_hint && !strncmp(pv->device_hint, "/dev/md", 7))
 				do_full_check = 1;
 		}
-		if (do_full_check && dev_is_md_component(dev, NULL, 1)) {
+		if (do_full_check && dev_is_md_component(cmd, dev, NULL, 1)) {
 			log_print("pvscan[%d] ignore md component %s.", getpid(), dev_name(dev));
 			release_vg(vg);
 			continue;