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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.)
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!
We can't use 'DM_SBIN_PATH'. This one is set only for DM devices but not
for all block devices - the pvscan is run on all relevant block devices!
This LVM_SBIN_PATH (as well as DM_SBIN_PATH) detection should be removed
eventually but for upstream solution, we still have to do that as there are
known cases where the binaries are put either in /sbin or /usr/sbin
(some installation systems, initrd systems etc.).
Why using the order 69:
- Storage processing in general happens in 60-persistent-storage.rules,
including the blkid call that adds some usable information we can use
for filtering and speedup (these rules are part of upstream udev and
the order is preserved on most distros)
- There's still some other storage-related processing done after
60-persistent-storage.rules in general. These might add some detailed
storage-related information we might use to filter devices effectively
(e.g. MD udev rules, ...).
- We need lvmetad rules to be processed before any consumers can use the
output - so the metadata cache is ready soon enough (e.g. udisks rules).
- There's no official (upstream udev) document about assigning the order,
so this number is chosen in best belief it will suit all scenarios.
We don't have anything better yet...
The problems the watch rule caused when removing devices should be covered
now with the "retry remove" logic. It's also better to have this maintained
by us, rather than having this rule anywhere else without proper control.
Skip decoding of DM flags when device is removed.
We currently need DM flags only for add|change events. So forking
dmsetup process for removed devices is a waste of CPU time.
Udev is already quite slow, so make it just a tiny bit faster.
This is to avoid any scanning and processing of DM devices while they are in
suspended state (e.g. a rename while the device is suspended - a CHANGE event
is generated!). Otherwise, any scanning in the rules could end up with locking
the calling process until the device is resumed and so we don't receive a
notification about udev rules completion until then (and that effectively
locks out the process awaiting the notification!).
However, we still keep 'disk' and any 'subsystem' related udev rules running.
We trust these and these should check themselves whether a device is suspended
or not, not trying to run any scanning if it is.
This can happen with older rules (without support for synthesized events)
that are still part of initrd while using new udev rules in the system itself.
The consequence was that new udev rules incorrectly assumed that not having
DM_UDEV_PRIMARY_SOURCE_FLAG set always means the uevent is synthesized and
inappropriate (device is still not properly activated) and so it should be
ignored. However, initrd is not updated automatically while updating the
libdevmapper/udev rules in the system and so we end up with the rules not
detecting and setting crucial parts in the initrd environment and the rules
in the system that rely on the information that should have been stored in
udev db (which is incorrect in this configuration, of course).
The overall consequence is that the update of libdevmapper/lvm2 without
regenerating the initrd could end up with a boot failure! Ignoring the event
means removing any existing symlinks in /dev!
To fix this, increase udev rules version to make a difference. So from now on,
mark rules without proper support for synthesized events as
DM_UDEV_RULES_VSN="1" and 2 (or higher) if that support is included.
We still need to detect this one! We're not so strict with CHANGE events as
with the ADD events while applying filters in the rules so this one would
pass and it would process the rules prematurely (because it appears *before*
the actual CHANGE event used when resuming a DM device while setting read-only
state at the same time).
For now, this is just a precaution. Normally, all the other (non-dm) rules
should check DM_UDEV_DISABLE_OTHER_RULES_FLAG and therefore avoid setting
any inotify watches as well. But let's make sure.
Support for final assignment of the "nowatch" rule (the use of ":=") will
appear in next udev release, v160. This should also work in previous udev
versions but the setting won't be sealed so any further OPTIONS="watch" will
always prevail there.
We may want to add more specific "nowatch" rules later if needed.
We can use DM_UDEV_PRIMARY_SOURCE_FLAG to identify the spurious events
and use it as an indication that the device has already been activated before
(and hence we can find this property in udev database).
WARNING: This change requires udev startup script to preserve udev database
from initrd. All the information stored there during activation of devices
is important for the initial "udevadm trigger --action=add" call that is
used in udev startup script. If not done this way, udev startup script needs
to define DM_UDEV_PRIMARY_SOURCE_FLAG=1 property for any ADD events it uses.
This rule appeared in udev v152 and it helps us to support spurious events
where we didn't have any flags set (events originated in udevadm trigger
or the watch rule). These flags are important to direct the rule application.
Now, with the help of this rule, we can regenerate old udev db content.
To implement this correctly, we need to flag all proper DM udev events with
DM_UDEV_PRIMARY_SOURCE_FLAG. That happens automatically for all ioctls
generating events originated in libdevmapper.
Fix unwanted modification of $(top_builddir)/make.tmpl.
Using dependency rules to install rules for udev.
There is minor problem, with concurent usage of builddir
and srcdir could lead to missuse of 10-dm.rules which
could be found in VPATH from different builddir.
However current solution uses intermediate target so
the generated 10-dm.rules exists only for short period of time
during make install execution.
Usage of VPATH makes troubles when used within $(builddir).
Not only source files are being found through VPATH,
but targets as well. (make --debug=v)
Thus if user builds the code in $(srcdir) and also in some $(builddir)
he gets mangled results as some generated files (i.e. .export.sym)
are 'reused' from $(srcdir) instead of $(builddir).
This patch switches to use vpath were we could explicitly name
suffixes that should be looked via vpath - we must take care,
we do not generate files with these suffixes:
.c, .in, .po, .exported_symbols
There's a tiny period of time when the _mimage device is visible during
downconversion from mirror to linear. Since it is visible, we need to
create the symlinks, otherwise warning messages will be issued about udev
not creating those symlinks. We have to rely on udev flags completely.
There's a new change udev event generated since kernel 2.6.32 that
notifies userspace about a change in read-only attribute for block
devices (with DISK_RO=1 environment variable set).
We need to detect this and disable the rule application so the
meaning of this change event is not interchanged with the regular
change event used while resuming/renaming DM devices.
If there's anybody awaiting this notification in foreign rules,
he can still check for this env var and do the appropriate actions
separately.
'last_rule' option has been removed from udev (version >= 147).
From now on, we require foreign rules to check and honor
ENV{DM_UDEV_DISABLE_OTHER_RULES_FLAG} instead. Foreign
rules should be skipped totally when this flag is set.
- add copyright notice for 10-dm.rules.in,
- set DM_UDEV_DISABLE_{DISK, OTHER}_RULES_FLAG in 11-dm-lvm.rules directly
for inappropriate and non-top-level subdevices in case we use older kernels
where DM_COOKIE is not used (and therefore there are no flags passed from
the LVM process itself). This applies for older kernels (version < 2.6.31),
- remove unnecessary filters in 95-dm-notify.rules - the DM_COOKIE env var
itself is set for change/remove udev events and for DM devices only so
there's no need to double-check this.
- we have these levels when the udev rules are processed:
10-dm.rules --> [11-dm-<subsystem>.rules] --> [12-dm-permissions.rules] -->
13-dm-disk.rules --> [...all the other foreign rules...] --> 95-dm-notify.rules
- each level can be disabled now by
DM_UDEV_DISABLE_{DM, SUBSYSTEM, DISK, OTHER}_RULES_FLAG
- add DM_UDEV_DISABLE_DM_RULES_FLAG to disable 10-dm.rules
- add DM_UDEV_DISABLE_OTHER_RULES_FLAG to disable all the other (non-dm) rules.
We cutoff these rules by using the 'last_rule', so this one should really be
used with great care and in well-founded situations. We use this for lvm's
hidden and layer devices now.
- add a parameter for add_dev_node, rm_dev_node and rename_dev_node so it's
possible to switch on/off udev checks
- use DM_UDEV_DISABLE_DM_RULES_FLAG and DM_UDEV_DISABLE_SUBSYSTEM_RULES_FLAG
if there's no cookie set and we have resume, remove and rename ioctl.
This could happen when someone uses the libdevmapper that is compiled with
udev_sync but the software does not make use of it. This way we can switch
off the rules and fallback to libdevmapper node creation so there's no
udev/libdevmapper race.
- remove default permissions set in 95-dm-notify.rules (and add a hint in 12-dm-permissions.rules to set it by the user directly)
- add multipath DM_ACTION=="PATH_FAILED" filter
- remove unnecessary filters in the headers of the rules (we can simply use DM_UDEV_RULES_VSN instead)
- fix symlink priorities in /dev/disk/ (snapshot volumes have low priority for FS UUID symlinks so it will not overwrite symlinks for the origin)
- add DM_UDEV_RULES_VSN to provide a variable to be checked for in the other
rules (e.g. to check that DM rules are actually installed, we can alternate
functionality in the other rules based on this information, also we have
versioning support for the rules)
- set proper sbin path for dmsetup and blkid, /sbin first, then /usr/sbin.
This is necessary for anaconda to work properly.
- add 'last_rule' for cryptsetup's temporary devices (symlinks in /dev/mapper
only)
