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Commit 756bcabbfe restricted the
situations at which the LVM autoactivation fires - only on ADD
event for devices other than DM. However, this caused a problem
for MD devices...
MD devices are activated in a very similar way as DM devices:
the MD dev is created on first appeareance of MD array member
(ADD event) and stays *inactive* until the array is complete.
Just then the MD dev turns to active state and this is reported
to userspace by CHANGE event.
Unfortunately, we can't differentiate between the CHANGE event
coming from udev trigger/WATCH rule and CHANGE event coming from
the transition to active state - MD would need to add similar logic
we already use to detect this in DM world. For now, we just have
to enable pvscan --cache on *all* CHANGE events for MD so the
autoactivation of the LVM volumes on top of MD works.
A downside of this is that a spurious CHANGE event for MD dev
can cause the LVM volumes on top of it to be automatically activated.
However, one should not open/change the device underneath until
the device above in the stack is removed! So this situation should
only happen if one opens the MD dev for read-write by mistake
(and hence firing the CHANGE event because of the WATCH udev rule),
or if calling udev trigger manually for the MD dev.
(No WHATS_NEW here as this fixes the commit mentioned
above and which has not been released yet.)
Commit 756bcabbfe fixed autoactivation
to not trigger on each uevent for a PV that appeared in the system
most notably the events that are triggered artificially (udevadm
trigger or as the result of the WATCH udev rule being applied that
consequently generates CHANGE uevents). This fixed a situation in
which VGs/LVs were activated when they should not.
BUT we still need to care about the coldplug used at boot to
retrigger the ADD events - the "udevadm trigger --action=add"!
For non-DM-based PVs, this is already covered as for these we
run the autoactivation on ADD event only.
However, for DM-based PVs, we still need to run the
autoactivation even for the artificial ADD event, reusing
the udev DB content from previous proper CHANGE event that
came with the DM device activation.
Simply, this patch fixes a situation in which we run extra
"udevadm trigger --action=add" (or echo add > /sys/block/<dev>/uevent)
for DM-based PVs (cryptsetup devices, multipath devices, any
other DM devices...).
Without this patch, while using lvmetad + autoactivation,
any VG/LV that has a DM-based PV and for which we do not
call the activation directly, the VG/LV is not activated.
For example a VG with an LV with root FS on it which is directly
activated in initrd and then missing activation of the rest
of the LVs in the VG because of unhandled uevent retrigger on
boot after switching to root FS (the "coldplug").
(No WHATS_NEW here as this fixes the commit mentioned
above and which was not released yet.)
Before, the pvscan --cache -aay was called on each ADD and CHANGE
uevent (for a device that is not a device-mapper device) and each CHANGE
event (for a PV that is a device-mapper device).
This causes troubles with autoactivation in some cases as CHANGE event
may originate from using the OPTION+="watch" udev rule that is defined
in 60-persistent-storage.rules (part of the rules provided by udev
directly) and it's used for all block devices
(except fd*|mtd*|nbd*|gnbd*|btibm*|dm-*|md* devices). For example, the
following sequence incorrectly activates the rest of LVs in a VG if one
of the LVs in the VG is being removed:
[root@rhel6-a ~]# pvcreate /dev/sda
Physical volume "/dev/sda" successfully created
[root@rhel6-a ~]# vgcreate vg /dev/sda
Volume group "vg" successfully created
[root@rhel6-a ~]# lvcreate -l1 vg
Logical volume "lvol0" created
[root@rhel6-a ~]# lvcreate -l1 vg
Logical volume "lvol1" created
[root@rhel6-a ~]# vgchange -an vg
0 logical volume(s) in volume group "vg" now active
[root@rhel6-a ~]# lvs
LV VG Attr LSize Pool Origin Data% Move Log
Cpy%Sync Convert
lvol0 vg -wi------ 4.00m
lvol1 vg -wi------ 4.00m
[root@rhel6-a ~]# lvremove -ff vg/lvol1
Logical volume "lvol1" successfully removed
[root@rhel6-a ~]# lvs
LV VG Attr LSize Pool Origin Data% Move Log
Cpy%Sync Convert
lvol0 vg -wi-a---- 4.00m
...so the vg was deactivated, then lvol1 removed, and we end up with
lvol1 removed (which is ok) BUT with lvol0 activated (which is wrong)!!!
This is because after lvol1 removal, we need to write metadata to the
underlying device /dev/sda and that causes the CHANGE event to be
generated (because of the WATCH udev rule set on this device) and this
causes the pvscan --cache -aay to be reevaluated.
We have to limit this and call pvscan --cache -aay to autoactivate
VGs/LVs only in these cases:
--> if the *PV is not a dm device*, scan only after proper device
addition (ADD event) and not with any other changes (CHANGE event)
--> if the *PV is a dm device*, scan only after proper mapping
activation (CHANGE event + the underlying PV in a state "just
activated")
Define auto_activation_handler that activates VGs/LVs automatically
based on the activation/auto_activation_volume_list (activating all
volumes by default if the list is not defined).
The autoactivation is done within the pvscan call in 69-dm-lvmetad.rules
that watches for udev events (device appearance/removal).
For now, this works for non-clustered and complete VGs only.
Remove executable path detection in udev rules and use sbindir that
is configured, but still provide the original functionality by means
of 'configure --enable-udev-rule-exec-detection'.
Normally, the exec path for the tools called in udev rules should
not differ from the sbindir used, however, there are cases this is
necessary. For example different environments could be assembled
in a way that these path differ for some reason (distribution installer,
initrd ...).
This functionality is kept for compatibility only. Any environment
moving the binaries around and using different paths should be fixed
eventually!
