vgchange -aay: optimize device scan using pvs_online files

Port the old pvscan -aay scanning optimization to vgchange -aay.
The optimization uses pvs_online files created by pvscan --cache
to derive a list of devices to use when activating a VG.  This
allows autoactivation of a VG to avoid scanning all devices, and
only scan the devices used by the VG itself.  The optimization is
applied internally using the device hints interface.

The new option "--autoactivation event" is given to pvscan and
vgchange commands that are called by event activation.  This
informs the command that it is being used for event activation,
so that it can apply checks and optimizations that are specific
to event activation.  Those include:

- skipping the command if lvm.conf event_activation=0
- checking that a VG is complete before activating it
- using pvs_online files to limit device scanning

1 files changed, 6 insertions, 0 deletions

diff --git a/tools/args.h b/tools/args.h
index 774ce33f4..2aed8afbb 100644
--- a/tools/args.h
+++ b/tools/args.h
@@ -87,6 +87,12 @@ arg(atversion_ARG, '\0', "atversion", string_VAL, 0, 0,
     "which does not contain any newer settings for which LVM would\n"
     "issue a warning message when checking the configuration.\n")
 
+arg(autoactivation_ARG, '\0', "autoactivation", string_VAL, 0, 0,
+    "Specify if autoactivation is being used from an event.\n"
+    "This allows the command to apply settings that are specific\n"
+    "to event activation, such as device scanning optimizations\n"
+    "using pvs_online files created by event-based pvscans.\n")
+
 arg(setautoactivation_ARG, '\0', "setautoactivation", bool_VAL, 0, 0,
     "Set the autoactivation property on a VG or LV.\n"
     "Display the property with vgs or lvs \"-o autoactivation\".\n"