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An OS installer can create system.devices for the system and
disks, but an OS image cannot create the system-specific
system.devices. The OS image can instead configure the
image so that lvm will create system.devices on first boot.
Image preparation steps to enable auto creation of system.devices:
- create empty file /etc/lvm/devices/auto-import-rootvg
- remove any existing /etc/lvm/devices/system.devices
- enable lvm-devices-import.path
- enable lvm-devices-import.service
On first boot of the prepared image:
- udev triggers vgchange -aay --autoactivation event <rootvg>
- vgchange activates LVs in the root VG
- vgchange finds the file /etc/lvm/devices/auto-import-rootvg,
and no /etc/lvm/devices/system.devices, so it creates
/run/lvm/lvm-devices-import
- lvm-devices-import.path is run when /run/lvm/lvm-devices-import
appears, and triggers lvm-devices-import.service
- lvm-devices-import.service runs vgimportdevices --rootvg --auto
- vgimportdevices finds /etc/lvm/devices/auto-import-rootvg,
and no system.devices, so it creates system.devices containing
PVs in the root VG, and removes /etc/lvm/devices/auto-import-rootvg
and /run/lvm/lvm-devices-import
Run directly, vgimportdevices --rootvg (without --auto), will create
a new system.devices for the root VG, or will add devices for the
root VG to an existing system.devices.
Instead of storing command_id as string, direcly
translate string to enum index and use 'command_enum()'
to get string when needed for printing.
This way we can easily detect error in the structure
while parsing it - and we can later avoid separate
'translation' loop.
pvs -A|--allpvs
Show PVs that would otherwise be excluded by the devices file.
pvscan -A|--allpvs
Show PVs that would otherwise be excluded by the devices file.
For those devices that are included by the devices file,
their device ID is displayed in place of the usual "lvm2"
format and size.
(pvs -a|--all is unchanged, and shows devices not formatted as PVs.)
If the system changes, locate PVs that appear on different devices,
and update the device IDs in the devices file. A system change is
detected by saving the DMI product_uuid or hostname in the devices
file, and comparing it to the current system value. If a root PV
is restored or copied to a new system with different devices, then
the product_uuid or hostname should change, and trigger lvm to
locate PVIDs from system.devices on new devices.
This was trying to warn about a misconfig where the root PV
was excluded by the devices file, but it wasn't covering all
cases. Also, it's not very useful because the root LV is
usually activated directly in the initrd.
With the recent use of DEVLINKS, there is no longer any real
point in checking the filter for symlink names. Removing
this check should not change behavior with or without symlinks
in the filter.
"vgchange -aay --autoactivation event" is called by our udev rule.
When the udev rule runs, symlinks for devices may not all be created
yet. If the regex filter contains symlinks, it won't work correctly.
This command uses devices that already passed through pvscan. Since
pvscan applies the regex filter correctly, this command inherits the
filtering from pvscan and can skip the regex filter itself.
See the previous commit
"pvscan: use alternate device names from DEVLINKS to check filter"
pvscan --cache <dev> is called by our udev rule at a time when all
the symlinks for <dev> may not be created yet (by other udev rules.)
The regex filter in lvm.conf may refer to <dev> using a symlink name
that hasn't yet been created, which would cause <dev> to not match
the filter regex. The DEVLINKS env var, set by udev, contains all
the symlink names for <dev> that have been or will be created.
So, we add all these symlink names to dev->aliases, as if we had
found them in /dev. This allows <dev> to be recognized by a regex
filter containing a symlink for <dev>.
These files are automatically cleared on reboot given
that /run is tmpfs, and that remains the primary way
of clearing online files.
But, if there's extreme use of vgcreate+pvscan+vgremove
between reboots, then removing online files in vgremove
will limit the number of unused online files using space
in /run.
In most installations, /dev/sda* or /dev/vda* should be included
in system.devices because the root, home, etc LVs are usually on
sda or vda.
Add a special case warning when a pvscan autoactivation command
sees that /dev/sda* or /dev/vda* are excluded by system.devices,
either not listed or having a different device id.
Change messages that refer to devices being "excluded by filters"
to say just "excluded". This will avoid mistaking the word
"filters" with the lvm.conf filter setting.
Fixes commit "pvscan: match device arg to filter symlink"
which failed to account for the fact that filter entries
are not just path names but include "a" or "r", etc.
The device_hint name in the metadata was meant to prevent
autoactivation from md components, but the name checks were
more general and would catch unnecessary cases.
This fixes an issue related to the optimization in
"pvscan: only add device args to dev cache"
If the devices file is not used, and the lvm.conf filter
accepts devices via symlink names, then those devices won't
be accepted by pvscan for autoactivation. To resolve this,
recognize when the filter contains symlinks and disable the
optimization. When the optimization is disabled, a full
dev_cache_scan is performed, and symlinks are associated
with the device names passed to pvscan. filter-regex
will accept a device if symlinks to that device are accepted.
Consistently create the pvs_lookup file for VGs with
more than one PV. Previously the file create would be
skipped if all the PVs happened to already be online.
That led to unpredicatable results in an uncommon case
(when the last PV to come online is the only PV with
metadata.)
Include the device name in the /run/lvm/pvs_online/pvid files.
Commands using the pvid file can use the devname to more quickly
find the correct device, vs finding the device using the
major:minor number. If the devname in the pvid file is missing
or incorrect, fall back to using the devno.
Port another optimization from pvscan -aay to vgchange -aay:
"pvscan: only add device args to dev cache"
This optimization avoids doing a full dev_cache_scan, and
instead populates dev-cache with only the devices in the
VG being activated.
This involves shifting the use of pvs_online files from
the hints interface up to the higher level label_scan
interface. This specialized label_scan is structured
around creating a list of devices from the pvs_online
files. Previously, a list of all devices was created
first, and then reduced based on the pvs_online files.
The initial step of listing all devices was slow when
thousands of devices are present on the system.
This optimization extends the previous optimization that
used pvs_online files to limit the devices that were
actually scanned (i.e. reading to identify the device):
"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
The information in /run/lvm/pvs_online/<pvid> files can
be used to build a list of devices for a given VG.
The pvscan -aay command has long used this information to
activate a VG while scanning only devices in that VG, which
is an important optimization for autoactivation.
This patch implements the same thing through the existing
device hints interface, so that the optimization can be
applied elsewhere. A future patch will take advantage of
this optimization in vgchange -aay, which is now used in
place of pvscan -aay for event activation.
Resolve event_activation configure option just once.
Do not print debug_devs about 'bad' filtering, when
actually filter already printed reason for skipping
Do not trace more then once about backup being disabled.
No debug when unlinked file does not exists in pvscan.
pvscan --cache <dev>
. read only dev
. create online file for dev
pvscan --listvg <dev>
. read only dev
. list VG using dev
pvscan --listlvs <dev>
. read only dev
. list VG using dev
. list LVs using dev
pvscan --cache --listvg [--checkcomplete] <dev>
. read only dev
. create online file for dev
. list VG using dev
. [check online files and report if VG is complete]
pvscan --cache --listlvs [--checkcomplete] <dev>
. read only dev
. create online file for dev
. list VG using dev
. list LVs using dev
. [check online files and report if VG is complete]
. [check online files and report if LVs are complete]
[--vgonline]
can be used with --checkcomplete, to enable use of a vg online
file. This results in only the first pvscan command to see
the complete VG to report 'VG complete', and others will report
'VG finished'. This allows the caller to easily run a single
activation of the VG.
[--udevoutput]
can be used with --cache --listvg --checkcomplete, to enable
an output mode that prints LVM_VG_NAME_COMPLETE='vgname' that
a udev rule can import, and prevents other output from the
command (other output causes udev to ignore the command.)
The list of complete LVs is meant to be passed to lvchange -aay,
or the complete VG used with vgchange -aay.
When --checkcomplete is used, lvm assumes that that the output
will be used to trigger event-based autoactivation, so the pvscan
does nothing if event_activation=0 and --checkcomplete is used.
Example of listlvs
------------------
$ lvs -a vg -olvname,devices
LV Devices
lv_a /dev/loop0(0)
lv_ab /dev/loop0(1),/dev/loop1(1)
lv_abc /dev/loop0(3),/dev/loop1(3),/dev/loop2(1)
lv_b /dev/loop1(0)
lv_c /dev/loop2(0)
$ pvscan --cache --listlvs --checkcomplete /dev/loop0
pvscan[35680] PV /dev/loop0 online, VG vg incomplete (need 2).
VG vg incomplete
LV vg/lv_a complete
LV vg/lv_ab incomplete
LV vg/lv_abc incomplete
$ pvscan --cache --listlvs --checkcomplete /dev/loop1
pvscan[35681] PV /dev/loop1 online, VG vg incomplete (need 1).
VG vg incomplete
LV vg/lv_b complete
LV vg/lv_ab complete
LV vg/lv_abc incomplete
$ pvscan --cache --listlvs --checkcomplete /dev/loop2
pvscan[35682] PV /dev/loop2 online, VG vg is complete.
VG vg complete
LV vg/lv_c complete
LV vg/lv_abc complete
Example of listvg
-----------------
$ pvscan --cache --listvg --checkcomplete /dev/loop0
pvscan[35684] PV /dev/loop0 online, VG vg incomplete (need 2).
VG vg incomplete
$ pvscan --cache --listvg --checkcomplete /dev/loop1
pvscan[35685] PV /dev/loop1 online, VG vg incomplete (need 1).
VG vg incomplete
$ pvscan --cache --listvg --checkcomplete /dev/loop2
pvscan[35686] PV /dev/loop2 online, VG vg is complete.
VG vg complete
pvid and vgid are sometimes a null-terminated string, and
other times a 'struct id', and the two types were often
cast between each other. When a struct id was cast to a char
pointer, the resulting string would not necessarily be null
terminated. Casting a null-terminated string id to a
struct id is fine, but is still avoided when possible.
A struct id is: int8_t uuid[ID_LEN]
A string id is: char pvid[ID_LEN + 1]
A convention is introduced to help distinguish them:
- variables and struct fields named "pvid" or "vgid"
should be null-terminated strings.
- variables and struct fields named "pv_id" or "vg_id"
should be struct id's.
- examples:
char pvid[ID_LEN + 1];
char vgid[ID_LEN + 1];
struct id pv_id;
struct id vg_id;
Function names also attempt to follow this convention.
Avoid casting between the two types as much as possible,
with limited exceptions when known to be safe and clearly
commented.
Avoid using variations of strcpy and strcmp, and instead
use memcpy/memcmp with ID_LEN (with similar limited
exceptions possible.)
The lvm2-pvscan service runs pvscan --cache -aay <dev> for
device addition, and pvscan --cache <dev> on device removal.
For event_activation=0, the addition does nothing. Fix
device removal to also do nothing for event_activation=0.
Device removal was previously doing some work to process
the removal which slowed down stopping lvm2-pvscan services.
related to config settings:
obtain_device_info_from_udev (controls if lvm gets
a list of devices from readdir /dev or from libudev)
external_device_info_source (controls if lvm asks
libudev for device information)
. Make the obtain_device_list_from_udev setting
affect only the choice of readdir /dev vs libudev.
The setting no longer controls if udev is used for
device type checks.
. Change obtain_device_list_from_udev default to 0.
This helps avoid boot timeouts due to slow libudev
queries, avoids reported failures from
udev_enumerate_scan_devices, and avoids delays from
"device not initialized in udev database" errors.
Even without errors, for a system booting with 1024 PVs,
lvm2-pvscan times improve from about 100 sec to 15 sec,
and the pvscan command from about 64 sec to about 4 sec.
. For external_device_info_source="none", remove all
libudev device info queries, and use only lvm
native device info.
. For external_device_info_source="udev", first check
lvm native device info, then check libudev info.
. Remove sleep/retry loop when attempting libudev
queries for device info. udev info will simply
be skipped if it's not immediately available.
. Only set up a libdev connection if it will be used by
obtain_device_list_from_udev/external_device_info_source.
. For native multipath component detection, use
/etc/multipath/wwids. If a device has a wwid
matching an entry in the wwids file, then it's
considered a multipath component. This is
necessary to natively detect multipath
components when the mpath device is not set up.
dev_cache_index_devs() is taking a large amount of time
when there are many PVs. The index keeps track of
devices that are currently in use by active LVs. This
info is used to print warnings for users in some limited
cases.
The checks/warnings that are enabled by the index are not
needed by pvscan --cache, so disable it in this case.
This may be expanded to other cases in future commits.
dev_cache_index_devs should also be improved in another
commit to avoid the extreme delays with many devices.
error reading dev and no pvid on dev were both
returning 0. make it easier for callers to
know which, if they care.
return 1 if the device could be read, regardless
of whether a pvid was found or not.
set has_pvid=1 if a pvid is found and 0 if no
pvid is found.
