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If a dm device is suspended, we can't run blkid on it. But earlier
rules (e.g. 11-dm-parts.rules) might have imported previously scanned
properties from the udev db, in particular if the device had been correctly
set up beforehand (DM_UDEV_PRIMARY_SOURCE_FLAG==1). Symlinks for existing
ID_FS_xyz properties must be preserved in this case. Otherwise lower-priority
devices (such as multipath components) might take over the symlink
temporarily.
Likewise, we should't stop watching a temporarily suspended, but previously
correctly configured dm device.
Signed-off-by: Martin Wilck <mwilck@suse.com>
If the transient service remains after it's done, then
it prevents the same transient service from being run
again later if the PVs are detached and reattached
(although the behavior of a second autoactivation is not
well defined and may only work in limited cases.)
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
new udev rule 69-dm-lvm.rules replaces
69-dm-lvm-meta.rules and lvm2-pvscan.service
udev rule calls pvscan directly on the added device
pvscan output indicates if a complete VG can be activated
udev env var LVM_VG_NAME_COMPLETE is used to pass complete
VG name from pvscan to the udev rule
udev rule uses systemd-run to run vgchange -aay <vgname>
The OPTIONS+="event_timeout" is Unsupported since systemd/udev version 216,
that is ~5 years ago.
Since systemd/udev version 243, there's a new message printed if unsupported
OPTIONS value is used:
Invalid value for OPTIONS key, ignoring: 'event_timeout=180'
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1740666
We've been assigning this in 69-dm-lvm-metad.rules:
ENV{ID_MODEL}="LVM PV $env{ID_FS_UUID_ENC} on /dev/$name"
This was for the description to appear for each systemd device
unit representing this device, for example:
$systemctl -a | grep "LVM PV"
dev-block-252:2.device loaded active plugged LVM PV JhxC7B-YTgk-3jIU-5GVo-c4gV-W8t3-UUz06p on /dev/vda2 2
dev-disk-by\x2did-lvm\x2dpv\x2duuid\x2dJhxC7B\x2dYTgk\x2d3jIU\x2d5GVo\x2dc4gV\x2dW8t3\x2dUUz06p.device loaded active plugged LVM PV JhxC7B-YTgk-3jIU-5GVo-c4gV-W8t3-UUz06p on /dev/vda2 2
...
However, there could be an actual ID_MODEL that people are interested in
more than the fact that this is an LVM PV and so we shouldn't overwrite
the value.
Also, we already have a symlink /dev/disk/by-id/lvm-pv-uuid-<PV_UUID>
created which is then reflected as device unit (all device's symlinks
have systemd device unit representation) so we can still reach this
information in systemd unit listings even without setting the ID_MODEL.
Reported here: https://github.com/lvmteam/lvm2/issues/21
The current logic that avoids setting SYSTEMD_ALIAS and SYSTEMD_WANTS
on "change" events is flawed in the default "systemd background job"
configuration. For systemd, it's important that device properties don't
change spuriously.
If an "add" event starts lvm2-pvscan@.service for a device, and a
"change" event follows, removing SYSTEMD_ALIAS and SYSTEMD_WANTS from the
udev db, information about unit dependencies between the device and the
pvscan service can be lost in systemd, in particular if the daemon
configuration is reloaded.
Steps to reproduce problem:
- create a device with an LVM PV
- remove device
- add device (generates "add" and "change" uevents for the device)
(at this point SYSTEMD_ALIAS and SYSTEMD_WANTS are clear in udev db)
- systemctl daemon-reload
(systemd reloads udev db)
- vgchange -a n
- remove device
=> the lvm2-pvscan@.service for the device is still active although the
device is gone.
- add device again
=> the PV is not detected, because systemd sees the lvm2-pvscan@.service
as active and thus doesn't restart it.
The original purpose of this logic was to avoid volumes being scanned
over and over again. With systemd background jobs, that isn't necessary,
because systemd will not restart the job as long as it's active.
Signed-off-by: Martin Wilck <mwilck@suse.com>
Make the distinction between the cases with and without systemd
background jobs explicit in 69-dm-lvm-metad.rules rather than
substituting the rule from the Makefile. At this stage,
this improves only readibility, at the cost of one GOTO statement.
This patch introduces no functional change to the udev rules.
Signed-off-by: Martin Wilck <mwilck@suse.com>
The blkid we call in 13-dm-disk.rules also returns identifiers for
partitions based on which the /dev/disk/by-part{uuid,label} and
gpt-auto-root symlinks should be created in the same manner as we
already create symlinks for filesystem labels and uuids.
This is because we handle blkid calls and symlink creation under
/dev/disk ourselves in our 13-dm-disk.rules for device-mapper devices
for us to have more control over this process.
See also https://lists.freedesktop.org/archives/systemd-devel/2017-July/039220.html
and original report http://tracker.ceph.com/issues/19489 for
the exact case where these symlinks were missing.
Fixing vpath usage as it has been checking for existance of
generated file also in the $(scrdir) e.g.:
No need to remake target '10-dm.rules.in'; using VPATH name '...'
If the $(srcdir) had been also $(builddir) and contained already
generated rules file, it's been used instead generating new
one.
(See: http://make.mad-scientist.net/papers/how-not-to-use-vpath/)
If the PV label is lost (e.g. by doing a dd on the device), call
"systemd-run pvscan --cache <major>:<minor>" in 69-dm-lvm-metad.rules
to inform lvmetad about this state.
The reason for this is that ENV{SYSTEMD_WANTS}="lvm2-pvscan@<major>:<minor>"
logic will not cause the pvscan to be fired in this case since this works
only on proper device addition/removal cycle - the lvm2-pvscan service's
ExecStop is called only on proper REMOVE event - the service is bound to
device existence. Hence we need pvscan call via systemd-run (that
instantiates a quick transient service just to call the command).
See also https://bugzilla.redhat.com/show_bug.cgi?id=1063813.
We already have /dev/disk/by-id/dm-uuid-... (which encompasses the
VG UUID and LV UUID in case of LVs since the mapping's UUID is
VG+LV UUID together) and /dev/disk/by-id/dm-name-... (which encompasses
the VG and LV name in case of LVs).
This patch addds /dev/disk/by-id/lvm-pv-uuid-<PV_UUID> that completes
this scheme and makes navigation a bit easier using PV UUIDs since
one can navigate using PV UUIDs only and there's no need to do extra
PV UUID <--> kernel name matching (the PV UUID is stable across reboots).
This may come in handy in various scripts.
Since we already have the PV UUID stored in udev database (as a result
of blkid call - returned in ID_FS_UUID blkid's variable), this operation
is very cheap indeed, just creating the extra one symlink.
Clear temporary DM_DISABLE_OTHER_RULES_FLAG properly. This did not
cause any bug or problem as the temporary variable is overwritten next
time it's used again, but we should still clean it properly!
Do not drop device's flag to report readiness for systemd
processing if there's any event that follows the activatiion
event itself. Otherwise, systemd would lost track of this device
on any other event that follows the activating event (IOW, we
need to make SYSTEMD_READY variable change level-based, not edge-based).
This patch applies for MD and loop devices used as PVs.
(intra-release fix for commit 4c267c7286)
Some devices, similarly to us, are not prepared after ADD event, but
after an extra CHANGE event when the device is properly set up.
This includes MD and loop devices. This patch fixes the
SYSTEMD_READY assignment that is crucial for proper functionality
of SYSTEMD_WANTS that we use to instantiate a lvm2-pvscan@.service
systemd service to activate the VG/LVs (see also bug
info).
All that extra handling of foreign devices should eventually be moved
to rules which process those devices primarily (MD and loop)! We should
only check a dedicated variable whether the device is usable or not.
MD can directly create partition devices without a need to run
an extra kpartx or partprobe call. We need to react to this event in
a different way as for bare MD devices - we need to handle the ADD event
for KERNEL=="md[0-9]*p[0-9]*" kernel name and trigger the LVM scanning
to update lvmetad to trigger autoactivation and so on...
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1023250
Reset the DM_UDEV_OTHER_RULES_FLAG to original value right at the
time of dropping the DM_NOSCAN flag.
When DM_NOSCAN is set, the DM_UDEV_DISABLE_OTHER_RULES_FLAG is also set
to avoid udev processing in "other/foreign" rules. If the noscan flag
is dropped, the DM_UDEV_DISABLE_OTHER_RULES_FLAG should be reset to
its original value.
Also, lvmetad should respect the DM_UDEV_DISABLE_OTHER_RULES_FLAG
because if the volume is set with this flag it:
- definitely is not a top-level device (so makes no sense for lvmetad scanning)
- is not supposed to be scanned further (for any stacking on top of
it, including LVM stacking itself and any autoactivation of stacked LVs)
When using ENV{SYSTEMD_WANTS}=lvm2-pvscan@... to instantiate a service
for lvmetad scan when the new PV appears in the system, the service
is started and executed. However, to track device removal, we need
to bind it (the "BindsTo" systemd directive) to a certain .device
systemd unit.
In default systemd setup, the device is tracked by it's name and
sysfs path (there's normally a sysfs path .device systemd unit for
a device and then the device name .device unit as an alias for it).
Neither of these two is useful for lvmetad update as we need to bind
it to device's <major>:<minor> pair.
The /dev/block/<major>:<minor> is the essential symlink under /dev
that exists for each block device (created by default udev rules
provided by udev directly). So let's use this as an alias for
the device's .device unit as well by means of "ENV{SYSTEMD_ALIAS}"
declaration within udev rules which systemd understands (this will
create a new alias "dev-block-<major>:<minor>.device".
Then we can easily bind the "dev-block-<major>:<minor>" device
systemd unit with instantiated lvm2-pvscan@<major>:<minor>.service.
So once the device is removed from the systemd, the
lvm-pvscan@<major>:<minor>.service executes it's ExecStop action
(which in turn notifies lvmetad about the device being gone).
This completes the udev-systemd-lvmetad interaction then.
The new lvm2-pvscan@.service is responsible for on-demand execution
of "pvscan --cache --activate ay" which causes lvmetad to be
updated and LVM activation done if the VG is complete.
Also, use udev-systemd mechanism to instantiate the job as the
lvm2-pvscan@$devnode.service on each newly appeared PV in the system.
This prevents the background job to be killed (that would happen
if it was directly forked from udev rule - this behaviour is seen
in recent versions of udev with the help of systemd that can track
detached processes - the detached process would still be in the same
cgroup).
To enable this official udev-systemd protocol for instantiating
background jobs, use new --enable-udev-systemd-background-jobs
configure switch (it's disabled by default). This option is highly
recommended wherever systemd is used!
Recognize DM_SUBSYSTEM_UDEV_FLAG0 which for LVM is the "LVM_NOSCAN"
flag that causes the scanning to be skipped (mainly blkid) and
also directs all the foreign rules to be skipped as well.
Important thing here is that the "watch" udev rules is still set
as well as the /dev/disk/by-id content created (which does not
require any scanning to be done). Also, the flag is dropped on
any subsequent event and scanning done...
Each subsystem rule that needs to import any of DM_SUBSYSTEM_UDEV_FLAG*
flags is responsible for doing so. This simply moves control of these
flags from general 10-dm.rules to any subsystem rule using these flags
as each subsystem knows better how to handle these flags on its own.
The DM_ACTIVATION and DM_UDEV_PRIMARY_SOURCE_FLAG needs to be kept the
way it was for backward compatibility (e.g. the old rules are still
in initramfs). This way the check in whether the device should be
scanned in 69-dm-lvmetad.rules is even easier.
New versions of udev changed the default event timeout to 30s
from original 3min. This causes problems with LVM processes that
starve because of the IO load caused by some LVM actions (e.g.
mirror/raid synchronization).
Reinstate the 3min udev timeout for now until we optimize this
in a way that even the 30s timeout is sufficient.
This patch fixes the way the special devices are handled
(special in this context means that they're not usable
after the usual ADD event like other generic devices):
- DM and MD devices are pvscanned only when they are just set up.
This is the first CHANGE event that makes the device usable
(the DM_UDEV_PRIMARY_SOURCE_FLAG is set for DM and the
md/array_state sysfs attribute is present for MD).
Whether the device is activated is remembered via
DM_ACTIVATED (for DM) and LVM_MD_PV_ACTIVATED (for MD)
udev environment variable. This is then used to decide
whether we should fire the pvscan on ADD event to
support coldplugging. For any (artificial) ADD event
generated during coldplug, the device must be already
set up properly to fire the pvscan on it.
- Similar for loop devices. For loop devices, only CHANGE
events are relevant (so there's a CHANGE after the loop
device is set up as well as detached). Whether the loop
has just been activated is detected via loop/backing_file
sysfs attribute presence. The activation state is remembered
via LVM_LOOP_PV_ACTIVATED udev environment variable.
- Do not pvscan multipath device components (underlying paths).
- Do not pvscan RAID device components.
- Also, set LVM_SCANNED="1" udev environment variable for
debug purposes (it's visible in the lvmdump -u that takes
the current udev database). This variable is set once
the pvscan is triggered.
The table below summarises when the pvscan is triggered
(marked with X, X* means fire only if the special dev is properly set up):
| real ADD | real CHANGE | artificial ADD | artificial CHANGE | remove
=============================================================================
DM | | X | X* | | X
MD | | X | X* | |
loop | | X | X* | |
other | X | | X | | X
Udev daemon has recently introduced a limit on the number of udev
processes (there was no limit before). This causes a problem
when calling pvscan --cache -aay in lvmetad udev rules which
is supposed to activate the volumes. This activation is itself
synced with udev and so it waits for the activation to complete
before the pvscan finishes. The event processing can't continue
until this pvscan call is finished.
But if we're at the limit with the udev process count, we can't
instatiate any more udev processes, all such events are queued
and so we can't process the lvm activation event for which the
pvscan is waiting.
Then we're in a deadlock since the udev process with the
pvscan --cache -aay call waits for the lvm activation udev
processing to complete, but that will never happen as there's
this limit hit with the number of udev processes.
The process with pvscan --cache -aay actually times out eventually
(3min or 30sec, depends on the version of udev).
This patch makes it possible to run the pvscan --cache -aay
in the background so the udev processing can continue and hence
we can avoid the deadlock mentioned above.
In stacked environment where we have a PV layered on top of a
snapshot LV and then removing the LV, lvmetad still keeps information
about the PV:
[0] raw/~ $ pvcreate /dev/sda
Physical volume "/dev/sda" successfully created
[0] raw/~ $ vgcreate vg /dev/sda
Volume group "vg" successfully created
[0] raw/~ $ lvcreate -L32m vg
Logical volume "lvol0" created
[0] raw/~ $ lvcreate -L32m -s vg/lvol0
Logical volume "lvol1" created
[0] raw/~ $ pvcreate /dev/vg/lvol1
Physical volume "/dev/vg/lvol1" successfully created
[0] raw/~ $ lvremove -ff vg/lvol1
Logical volume "lvol1" successfully removed
[0] raw/~ $ pvs
No device found for PV BdNlu2-7bHV-XcIp-mFFC-PPuR-ef6K-yffdzO.
PV VG Fmt Attr PSize PFree
/dev/sda vg lvm2 a-- 124.00m 92.00m
[0] raw/~ $ pvscan --cache --major 253 --minor 3
Device 253:3 not found. Cleared from lvmetad cache.
This is because of the reactivation that is done just before
snapshot removal as part of the process (vg/lvol1 from the example above).
This causes a CHANGE event to be generated, but any scan done
on the LV does not see the original data anymore (in this case
the stacked PV label on top) and consequently the ID_FS_TYPE="LVM2_member"
(provided by blkid scan) is not stored in udev db anymore for the LV.
Consequently, the pvscan --cache is not run anymore as the dev is not
identified as LVM PV by the "LVM2_member" id - lvmetad loses this info
and still keeps records about the PV.
We can run into a very similar problem with erasing the PV label directly:
[0] raw/~ $ lvcreate -L32m vg
Logical volume "lvol0" created
[0] raw/~ $ pvcreate /dev/vg/lvol0
Physical volume "/dev/vg/lvol0" successfully created
[0] raw/~ $ dd if=/dev/zero of=/dev/vg/lvol0 bs=1M
dd: error writing '/dev/vg/lvol0': No space left on device
33+0 records in
32+0 records out
33554432 bytes (34 MB) copied, 0.380921 s, 88.1 MB/s
[0] raw/~ $ pvs
PV VG Fmt Attr PSize PFree
/dev/sda vg lvm2 a-- 124.00m 92.00m
/dev/vg/lvol0 lvm2 a-- 32.00m 32.00m
[0] raw/~ $ pvscan --cache --major 253 --minor 2
No PV label found on /dev/vg/lvol0.
This patch adds detection of this change from ID_FS_LABEL="LVM2_member"
to ID_FS_LABEL="<whatever_else>" and hence informing the lvmetad
about PV being gone.
If loop device is first configured on systems where /dev/loop-control
is used to dynamically create the loop device itself, there's an
ADD+CHANGE even generated. But next time the existing /dev/loop[0-9]*
is reused, there's only a CHANGE event since the device representing
it is already present in kernel (so no ADD event in this case).
We can't ignore this CHANGE event for loop devices! This is a regression
caused by 756bcabbfe. We already had
a similar problem with MD devices which was fixed by
2ac217d408 (but that one was
only an intra-release fix).
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.)
