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, 0 deletions

diff --git a/lib/Makefile.in b/lib/Makefile.in
index 900ae2f83..8b3eac60a 100644
--- a/lib/Makefile.in
+++ b/lib/Makefile.in
@@ -34,6 +34,7 @@ SOURCES =\
 	device/dev-ext.c \
 	device/dev-io.c \
 	device/dev-md.c \
+	device/dev-mpath.c \
 	device/dev-swap.c \
 	device/dev-type.c \
 	device/dev-luks.c \