pvscan: avoid full scan for activation

When an online PV completed a VG, the standard
activation functions were used to activate the VG.
These functions use a full scan of all devs.
When many pvscans are run during startup and need
to activate many VGs, scanning all devs from all
the pvscans can take a long time.

Optimize VG activation in pvscan to scan only the
devs in the VG being activated.  This makes use of
the online file info that was used to determine
the VG was complete.

The downside of this approach is that pvscan activation
will not detect duplicate PVs and block activation,
where a normal activation command (which scans all
devices) would.

1 files changed, 76 insertions, 32 deletions

diff --git a/test/shell/duplicate-pvs-md1.sh b/test/shell/duplicate-pvs-md1.sh
index 47b5bace0..ccd113f84 100644
--- a/test/shell/duplicate-pvs-md1.sh
+++ b/test/shell/duplicate-pvs-md1.sh
@@ -185,20 +185,28 @@ lvs -o active $vg |tee out || true
 grep "active" out
 vgchange -an $vg
 
-# N.B. pvscan --cache on the md component does not detect it's
-# a md component, and marks the PVID online, then does activation,
-# but the activation phase scans all devs, finds duplicates between
-# components and the actual md dev, chooses the md dev, and activates
-# the VG using the md dev.
-# The behavior with auto mode is preferable in which this does nothing,
-# but this is ok.
+# N.B. when the md dev (which is started) has not been scanned by
+# pvscan, then pvscan --cache on the md component does not detect it's
+# an md component, and marks the PVID online, then does activation,
+# but the activation using the component fails because the component
+# device is busy from being used in the md dev, and activation fails.
+# The default behavior in auto mode is preferrable.
 _clear_online_files
-pvscan --cache -aay "$dev1"
+not pvscan --cache -aay "$dev1"
+ls "$RUNDIR/lvm/pvs_online/$PVIDMD"
+ls "$RUNDIR/lvm/vgs_online/$vg"
+lvs -o active $vg |tee out || true
+not grep "active" out
+
+# pvscan activation from mddev first, then try from component which fails
+_clear_online_files
+pvscan --cache -aay "$mddev"
 ls "$RUNDIR/lvm/pvs_online/$PVIDMD"
 ls "$RUNDIR/lvm/vgs_online/$vg"
 lvs -o active $vg |tee out || true
 grep "active" out
-# FIXME: verify the LV is using the md dev and not the component
+not pvscan --cache -aay "$dev1"
+
 
 vgchange -an $vg
 vgremove -f $vg
@@ -266,6 +274,14 @@ aux cleanup_md_dev
 # md_component_checks: start (not auto)
 # mddev: stopped             (not started)
 #
+# N.B. This test case is just characterizing the current behavior, even
+# though the behavior it's testing for is not what we'd want to happen.
+# In this scenario, we have disabled/avoided everything that would
+# lead lvm to discover that dev1 is an md component, so dev1 is used
+# as the PV.  Multiple default settings need to be changed to get to
+# this unwanted behavior (md_component_checks,
+# obtain_device_list_from_udev), and other conditions also
+# need to be true (md device stopped).
 
 aux lvmconf 'devices/md_component_checks = "start"'
 
@@ -301,26 +317,37 @@ not grep "$dev2" $HINTS
 not lvchange -ay $vg/$lv1
 not lvs $vg
 
-# pvscan activation all does nothing
+# pvscan activation all does nothing because both legs are
+# seen as duplicates which triggers md component check which
+# eliminates the devs
 _clear_online_files
 pvscan --cache -aay
 not ls "$RUNDIR/lvm/pvs_online/$PVIDMD"
 not ls "$RUNDIR/lvm/vgs_online/$vg"
 
-# pvscan activation from md components does nothing
 _clear_online_files
-pvscan --cache -aay "$dev1" || true
-# N.B it would be preferrable if this did not recognize the PV on the
-# component and attempt to activate, like auto mode, but this is ok,
-# the activation scans all devs, sees duplicates, which triggers md
-# component detection which eliminates both devs, leaving no vg to activate.
+pvscan --cache -aay "$dev1"
 ls "$RUNDIR/lvm/pvs_online/$PVIDMD"
 ls "$RUNDIR/lvm/vgs_online/$vg"
-pvscan --cache -aay "$dev2" || true
-lvs -o active $vg |tee out || true
-not grep "active" out
 
-aux cleanup_md_dev
+# N.B. not good to activate from component, but result of "start" setting
+# Other commands will not see the vg at this point because they'll
+# recognize the md components and ignore them (where pvscan is special due
+# to it not scanning all devs and not seeing the duplicates and not
+# detecting the components.)
+# disable dev2 so other cmds don't see dups and we can deactivate the vg
+aux disable_dev "$dev2"
+vgchange -an $vg
+
+aux enable_dev "$dev2"
+aux udev_wait
+cat /proc/mdstat
+# for some reason enabling dev2 starts an odd md dev
+mdadm --stop "$mddev" || true
+mdadm --stop --scan
+cat /proc/mdstat
+wipefs -a "$dev1" || true
+wipefs -a "$dev2" || true
 
 
 ##########################################
@@ -382,12 +409,18 @@ _clear_online_files
 pvscan --cache -aay
 ls "$RUNDIR/lvm/pvs_online/$PVIDMD"
 ls "$RUNDIR/lvm/vgs_online/$vg"
+# N.B. not good to activate from component, but result of "start" setting
+lvs -o active $vg |tee out || true
+grep "active" out
 vgchange -an $vg
 
 _clear_online_files
 pvscan --cache -aay "$dev1"
 ls "$RUNDIR/lvm/pvs_online/$PVIDMD"
 ls "$RUNDIR/lvm/vgs_online/$vg"
+# N.B. not good to activate from component, but result of "start" setting
+lvs -o active $vg |tee out || true
+grep "active" out
 vgchange -an $vg
 
 aux enable_dev "$dev2"
@@ -582,21 +615,32 @@ pvscan --cache -aay
 not ls "$RUNDIR/lvm/pvs_online/$PVIDMD"
 not ls "$RUNDIR/lvm/vgs_online/$vg"
 
-# pvscan activation from md components does nothing
 _clear_online_files
 pvscan --cache -aay "$dev1" || true
-# N.B it would be preferrable if this did not recognize the PV on the
-# component and attempt to activate, like auto mode, but this is ok,
-# the activation scans all devs, sees duplicates, which triggers md
-# component detection which eliminates both devs, leaving no vg to activate.
 ls "$RUNDIR/lvm/pvs_online/$PVIDMD"
 ls "$RUNDIR/lvm/vgs_online/$vg"
-pvscan --cache -aay "$dev2" || true
-lvs -o active $vg |tee out || true
-not grep "active" out
-pvscan --cache -aay "$dev4" || true
-lvs -o active $vg |tee out || true
-not grep "active" out
+# N.B. not good to activate from component, but result of "start" setting
+# Scanning the other two legs sees existing pv online file and warns about
+# duplicate PVID, exiting with error:
+not pvscan --cache -aay "$dev2"
+not pvscan --cache -aay "$dev4"
+
+# Have to disable other legs so we can deactivate since
+# vgchange will detect and eliminate the components due
+# to duplicates and not see the vg.
+aux disable_dev "$dev2"
+aux disable_dev "$dev4"
+vgchange -an $vg
 
-aux cleanup_md_dev
+aux enable_dev "$dev2"
+aux enable_dev "$dev4"
+aux udev_wait
+cat /proc/mdstat
+# for some reason enabling dev2 starts an odd md dev
+mdadm --stop "$mddev" || true
+mdadm --stop --scan
+cat /proc/mdstat
+wipefs -a "$dev1" || true
+wipefs -a "$dev2" || true
+wipefs -a "$dev4" || true