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io_setup() for aio may fail if a system has reached the
aio request limit. In this case, fall back to using
sync io. Also, lvm use of aio can be disabled entirely
with config setting global/use_aio=0.
The system limit for aio requests can be seen from
/proc/sys/fs/aio-max-nr
The current usage of aio requests can be seen from
/proc/sys/fs/aio-nr
The system limit for aio requests can be increased by
setting fs.aio-max-nr using sysctl.
Also add last-byte limit to the sync io code.
When persistent_filter_create() fails, the existing passed filter
should be preserved, so it could be properly deleted on
error path - so new pfilter is assigned instead.
devices/scan_lvs (default 1) determines whether lvm
will scan LVs for layered PVs. The lvm behavior has
always been to scan LVs, but it's rare for LVs to have
layered PVs, and much more common for there to be many
LVs that substantially slow down scanning with no benefit.
This is implemented in the usable filter, and has the
same effect as listing all LVs in the global_filter.
Native disk scanning is now both reduced and
async/parallel, which makes it comparable in
performance (and often faster) when compared
to lvm using lvmetad.
Autoactivation now uses local temp files to record
online PVs, and no longer requires lvmetad.
There should be no apparent command-level change
in behavior.
It's no longer needed. Clustered VGs are now handled in
the same way as foreign VGs, and as shared VGs that
can't be accessed:
- A command processing all VGs sees a clustered VG,
prints a message ("Skipping clustered VG foo."),
skips it, and does not fail.
- A command where the clustered VG is explicitly
named on the command line, prints a message and fails.
"Cannot access clustered VG foo, see lvmlockd(8)."
The option is listed in the set of ignored options for
the commands that previously accepted it. (Removing it
entirely would cause commands/scripts to fail if they
set it.)
As we start refactoring the code to break dependencies (see doc/refactoring.txt),
I want us to use full paths in the includes (eg, #include "base/data-struct/list.h").
This makes it more obvious when we're breaking abstraction boundaries, eg, including a file in
metadata/ from base/
Filters are still applied before any device reading or
the label scan, but any filter checks that want to read
the device are skipped and the device is flagged.
After bcache is populated, but before lvm looks for
devices (i.e. before label scan), the filters are
reapplied to the devices that were flagged above.
The filters will then find the data they need in
bcache.
The clvmd saved_vg data is independent from the normal lvm
lvmcache vginfo data, so separate saved_vg from vginfo.
Normal lvm doesn't need to use save_vg at all, and in clvmd,
lvmcache changes on vginfo can be made without worrying
about unwanted effects on saved_vg.
There are likely more bits of code that can be removed,
e.g. lvm1/pool-specific bits of code that were identified
using FMT flags.
The vgconvert command can likely be reduced further.
The lvm1-specific config settings should probably have
some other fields set for proper deprecation.
The copy of VG metadata stored in lvmcache was not being used
in general. It pretended to be a generic VG metadata cache,
but was not being used except for clvmd activation. There
it was used to avoid reading from disk while devices were
suspended, i.e. in resume.
This removes the code that attempted to make this look
like a generic metadata cache, and replaces with with
something narrowly targetted to what it's actually used for.
This is a way of passing the VG from suspend to resume in
clvmd. Since in the case of clvmd one caller can't simply
pass the same VG to both suspend and resume, suspend needs
to stash the VG somewhere that resume can grab it from.
(resume doesn't want to read it from disk since devices
are suspended.) The lvmcache vginfo struct is used as a
convenient place to stash the VG to pass it from suspend
to resume, even though it isn't related to the lvmcache
or vginfo. These suspended_vg* vginfo fields should
not be used or touched anywhere else, they are only to
be used for passing the VG data from suspend to resume
in clvmd. The VG data being passed between suspend and
resume is never modified, and will only exist in the
brief period between suspend and resume in clvmd.
suspend has both old (current) and new (precommitted)
copies of the VG metadata. It stashes both of these in
the vginfo prior to suspending devices. When vg_commit
is successful, it sets a flag in vginfo as before,
signaling the transition from old to new metadata.
resume grabs the VG stashed by suspend. If the vg_commit
happened, it grabs the new VG, and if the vg_commit didn't
happen it grabs the old VG. The VG is then used to resume
LVs.
This isolates clvmd-specific code and usage from the
normal lvm vg_read code, making the code simpler and
the behavior easier to verify.
Sequence of operations:
- lv_suspend() has both vg_old and vg_new
and stashes a copy of each onto the vginfo:
lvmcache_save_suspended_vg(vg_old);
lvmcache_save_suspended_vg(vg_new);
- vg_commit() happens, which causes all clvmd
instances to call lvmcache_commit_metadata(vg).
A flag is set in the vginfo indicating the
transition from the old to new VG:
vginfo->suspended_vg_committed = 1;
- lv_resume() needs either vg_old or vg_new
to use in resuming LVs. It doesn't want to
read the VG from disk since devices are
suspended, so it gets the VG stashed by
lv_suspend:
vg = lvmcache_get_suspended_vg(vgid);
If the vg_commit did not happen, suspended_vg_committed
will not be set, and in this case, lvmcache_get_suspended_vg()
will return the old VG instead of the new VG, and it will
resume LVs based on the old metadata.
New label_scan function populates bcache for each device
on the system.
The two read paths are updated to get data from bcache.
The bcache is not yet used for writing. bcache blocks
for a device are invalidated when the device is written.
With pthreaded daemons like 'dmeventd' using liblvm via plugin,
lvm2 actually should not 'play' with streams at all - as there
could be parallel outputs running.
As a current quick workaround just disable change for pthreaded
program (gettid() != getpid()).
TODO: it's possible the change of buffering actually doesn't serve us
any measurable benefit and could be dropped as whole later...
Meanwhile this patch is fixing this occasional valgrind race report:
Invalid read of size 4
at 0x571892C: vfprintf (in /usr/lib64/libc-2.26.9000.so)
by 0x57216B3: fprintf (in /usr/lib64/libc-2.26.9000.so)
by 0x5042886: dm_event_log (libdevmapper-event.c:925)
by 0x10B015: _dmeventd_log (dmeventd.c:125)
by 0x10D289: _unregister_for_event (dmeventd.c:1146)
by 0x10E52E: _handle_request (dmeventd.c:1583)
by 0x10E6D7: _do_process_request (dmeventd.c:1631)
by 0x10E7C6: _process_request (dmeventd.c:1660)
by 0x1101A4: main (dmeventd.c:2285)
Address 0x6264d30 is 192 bytes inside a block of size 552 free'd
at 0x4C2ED68: free (vg_replace_malloc.c:530)
by 0x573907D: fclose@@GLIBC_2.2.5 (in /usr/lib64/libc-2.26.9000.so)
by 0x6AC5C00: reopen_standard_stream (log.c:189)
by 0x6A8E62C: destroy_toolcontext (toolcontext.c:2271)
by 0x6BA5C22: lvm_fin (lvmcmdline.c:3339)
by 0x6BD5EF3: lvm2_exit (lvmcmdlib.c:123)
by 0x6856013: dmeventd_lvm2_exit (dmeventd_lvm.c:103)
by 0x66535B8: unregister_device (dmeventd_thin.c:432)
by 0x10CBBC: _do_unregister_device (dmeventd.c:926)
by 0x10CD74: _monitor_unregister (dmeventd.c:979)
by 0x10D094: _monitor_thread (dmeventd.c:1066)
by 0x54B35E0: start_thread (in /usr/lib64/libpthread-2.26.9000.so)
by 0x57C30EE: clone (in /usr/lib64/libc-2.26.9000.so)
Block was alloc'd at
at 0x4C2DBBB: malloc (vg_replace_malloc.c:299)
by 0x573932B: fdopen@@GLIBC_2.2.5 (in /usr/lib64/libc-2.26.9000.so)
by 0x6AC5DC2: reopen_standard_stream (log.c:200)
by 0x6A8D11D: create_toolcontext (toolcontext.c:1898)
by 0x6BA5B6B: init_lvm (lvmcmdline.c:3319)
by 0x6BD5BC8: cmdlib_lvm2_init (lvmcmdlib.c:34)
by 0x6BD5F04: lvm2_init (lvm2cmd.c:20)
by 0x6855EA7: dmeventd_lvm2_init (dmeventd_lvm.c:67)
by 0x665305F: register_device (dmeventd_thin.c:352)
by 0x10CB7A: _do_register_device (dmeventd.c:916)
by 0x10CEE4: _monitor_thread (dmeventd.c:1006)
by 0x54B35E0: start_thread (in /usr/lib64/libpthread-2.26.9000.so)
by 0x57C30EE: clone (in /usr/lib64/libc-2.26.9000.so)
....
Process terminating with default action of signal 6 (SIGABRT): dumping core
at 0x570016B: raise (in /usr/lib64/libc-2.26.9000.so)
by 0x5701520: abort (in /usr/lib64/libc-2.26.9000.so)
by 0x57437D8: __libc_message (in /usr/lib64/libc-2.26.9000.so)
by 0x5743831: __libc_fatal (in /usr/lib64/libc-2.26.9000.so)
by 0x5744056: _IO_vtable_check (in /usr/lib64/libc-2.26.9000.so)
by 0x574751C: __overflow (in /usr/lib64/libc-2.26.9000.so)
by 0x574191A: fputc (in /usr/lib64/libc-2.26.9000.so)
by 0x50428E3: dm_event_log (libdevmapper-event.c:934)
by 0x10B015: _dmeventd_log (dmeventd.c:125)
by 0x10D289: _unregister_for_event (dmeventd.c:1146)
by 0x10E52E: _handle_request (dmeventd.c:1583)
by 0x10E6D7: _do_process_request (dmeventd.c:1631)
by 0x10E7C6: _process_request (dmeventd.c:1660)
by 0x1101A4: main (dmeventd.c:2285)
Make it easier to replace missing segments with 'zero' returning
target - otherwise user would have to create some extra target
to provide zeros as /dev/zero can't be used (not a block device).
Also break code loop when segment is found and make it an INTERNAL_ERROR
where it's missing.
We added lightweight toolcontext handle to avoid useless initialization
of some parts of the context and also to avoid problems when using the
handle very soon at system boot, like in lvm2-activation-generator
through lvm2app interface. However, we missed reading all the other
config sources like lvmlocal.conf as well as any tag config - we need to
read these too to get the final config value which may be overriden in
any of these additional config sources.
Currently, we use this lightweight toolcontext handle to read
global/use_lvmetad and global/use_lvmpolld config values in
lvm2-activation-generator using lvm2app interface (lvm_config_find_bool
lvm2app function).
Some settings are not suitable for override in interactive/shell
mode because such settings may confuse the code and it may end
up with unexpected behaviour. This is because of the fact that
once we're in the interactive/shell mode, we have already applied
some settings for the shell itself and we can't override them
further because we're already using those settings to drive the
interactive/shell mode. Such settings would get ignored silently
or, in worse case, they would mess up the existing configuration.
When lvm commands are executed in lvm shell, we cover the whole lvm
command execution within this shell now. That means, all messages logged
and status caught during each command execution is now recorded in the
log report, including overall command's return code.
With patches that will follow, this will make it possible to widen log
report coverage when commands are executed from lvm shell so the amount
of messages that may end up in stderr/stdout instead of log report are
minimized.
Currently, the output is separated in 3 parts and each part can go into
a separate and user-defined file descriptor:
- common output (stdout by default, customizable by LVM_OUT_FD environment variable)
- error output (stderr by default, customizable by LVM_ERR_FD environment variable)
- report output (stdout by default, customizable by LVM_REPORT_FD environment variable)
For example, each type of output goes to different output file:
[0] fedora/~ # export LVM_REPORT_FD=3
[0] fedora/~ # lvs fedora vg/abc 1>out 2>err 3>report
[0] fedora/~ # cat out
[0] fedora/~ # cat err
Volume group "vg" not found
Cannot process volume group vg
[0] fedora/~ # cat report
LV VG Attr LSize Layout Role CTime
root fedora -wi-ao---- 19.00g linear public Wed May 27 2015 08:09:21
swap fedora -wi-ao---- 500.00m linear public Wed May 27 2015 08:09:21
Another example in LVM shell where the report goes to "report" file:
[0] fedora/~ # export LVM_REPORT_FD=3
[0] fedora/~ # lvm 3>report
(in lvm shell)
lvm> vgs
(content of "report" file)
[1] fedora/~ # cat report
VG #PV #LV #SN Attr VSize VFree
fedora 1 2 0 wz--n- 19.49g 0
(in lvm shell)
lvm> lvs
(content of "report" file)
[1] fedora/~ # cat report
VG #PV #LV #SN Attr VSize VFree
fedora 1 2 0 wz--n- 19.49g 0
LV VG Attr LSize Layout Role CTime
root fedora -wi-ao---- 19.00g linear public Wed May 27 2015 08:09:21
swap fedora -wi-ao---- 500.00m linear public Wed May 27 2015 08:09:21
This fixes commit f50d4011cd which
introduced a problem when using older lvm2 code with newer libdm.
In this case, the old LVM didn't recognize new _LOG_BYPASS_REPORT flag
that libdm-report code used. This ended up with no output at all
from libdm where log_print_bypass_report was called because the
_LOG_BYPASS_REPORT was not masked properly in lvm2's print_log fn
which was called as callback function for logging.
With this patch, the lvm2 registers separate print_log_libdm logging
function for libdm instead. The print_log_libdm is exactly the same
as print_log (used throughout lvm2 code) but it checks whether we're
printing common line on output where "common" means not going to stderr,
not a warning and not an error and if we are, it adds the
_LOG_BYPASS_REPORT flag so the log_print goes directly to output, not
to any log report.
So this achieves the same goal as in f50d4011cd,
just doing it in a way that newer libdm is still compatible with older
lvm2 code (libdm-report is the only code using log_print).
Looking at the opposite mixture - older libdm with newer lvm2 code,
that won't be compilable because the new log report functionality
that is in lvm2 also requires new dm_report_group_* libdm functions
so we don't need to care here.
Some commands scan labels to populate lvmcache multiple
times, i.e. lvmcache_init, scan labels to fill lvmcache,
lvmcache_destroy, then later repeat
Each time labels are scanned, duplicates are detected,
and preferred devices are chosen. Each time this is done
within a single command, we want to choose the same
preferred devices. So, check for existing preferences
when choosing preferred devices.
This also fixes a problem with the list of unused duplicate
devs when run in an lvm shell. The devs had been allocated
from cmd memory, resulting in invalid list entries between
commands.
A program may be using liblvm2app for simply checking a config
setting in lvm.conf. In this case, a full lvm context is not
needed, only cmd->cft (which are the config settings read from
lvm.conf).
lvm_config_find_bool() can now be passed a NULL lvm context
in which case it will only create cmd->cft, check the config
setting asked for, and destroy the cmd.
When setting up a toolcontext, the lib init function
was detecting an error when there was none, and then
it was returning an incompletely initialized cmd struct
instead of NULL. The effect was that the lib would try
to use the uninitialized cmd struct and segfault.
This would happen if a non-fatal error occurred during
cmd setup, e.g. user permission failed on lvmetad socket,
causing cmd to fall back to scanning and not use lvmetad.
The only real error condition is when create_toolcontext
returns NULL. If cmd is returned, the lib can use it.
If lvmetad is running, and a command opts to not use it
(--config global/use_lvmetad=0), and the command changes
metadata, then the metadata change is not visible to
lvmetad. Subsequent commands using lvmetad to change
metadata may cause corruption based on the invalid
lvmetad state.
Eventually we can set the disabled state in lvmetad
to prevent this problem, but for now print a warning
about the possibility.
When command is not using lvmetad because
use_lvmetad=0 in the config, but the lvmetad
pidfile exists, print a warning (previously
this checked for the socket existing instead
of the pidfile existing.)
The lvmetad connection is created within the
init_connections() path during command startup,
rather than via the old lvmetad_active() check.
The old lvmetad_active() checks are replaced
with lvmetad_used() which is a simple check that
tests if the command is using/connected to lvmetad.
The old lvmetad_set_active(cmd, 0) calls, which
stopped the command from using lvmetad (to revert to
disk scanning), are replaced with lvmetad_make_unused(cmd).
When a command modifies a PV or VG, or changes the
activation state of an LV, it will send a dbus
notification when the command is finished. This
can be enabled/disabled with a config setting.
'verbose' was marked as a boolean option while it
takes integer args - so it has limited usage to 0 or 1,
but we supported 0-4 at least.
Fix it by switching to corrent int type.
(Hopefully noone was trying to use this variable as true/yes/false/no
way - as the would be unsupported/undocumented).
The regex filter (controlled by devices/filter lvm.conf setting) was
evaluated as the very last filter. However, this is not optimal when
it comes to restricting disk access - users define devices/filter
as well as devices/global_filter to avoid this.
The devices/global_filter is already positioned at the beginning of the
filter chain. We need to do the same for devices/filter.
Filter chains before this patch:
A: when lvmetad is not used:
persistent_filter -> sysfs_filter -> global_regex_filter ->
type_filter -> usable->filter -> mpath_component_filter ->
partition_filter -> md_component_filter -> fw_raid_filter ->
regex_filter
B: when lvmetad is used:
B1: to update lvmetad:
sysfs_filter -> global_regex_filter -> type_filter ->
usable_filter -> mpath_component_filter -> partition_filter ->
md_component_filter -> fw_raid_filter
B2: to retrieve info from lvmetad:
persistent_filter -> usable_filter -> regex_filter
From the chain list above we can see that particularly in case when
lvmetad is not used, the regex filter is the very last one that is
processed. If lvmetad is used, it doesn't matter much as there's
the global_regex_filter which is used instead when updating lvmetad
and when retrieving info from lvmetad, putting regex_filter in front
of usable_filter wouldn't change much since usabled_filter is not
reading disks directly.
This patch puts the regex filter to the front even in case lvmetad
is not used, hence reinstating the state as it was before commit
a7be3b12df (which moved the regex_filter
position in the chain). Still, the arguments for the commit
a7be3b12df still apply and they're
still satisfied since component filters (MD, mpath...) are evaluated
first just before updating lvmetad.
So with this patch, we end up with:
A: when lvmetad is not used:
persistent_filter -> sysfs_filter -> global_regex_filter ->
regex_filter -> type_filter -> usable->filter ->
mpath_component_filter -> partition_filter ->
md_component_filter -> fw_raid_filter
B: when lvmetad is used:
B1: to update lvmetad:
sysfs_filter -> global_regex_filter -> type_filter ->
usable_filter -> mpath_component_filter -> partition_filter ->
md_component_filter -> fw_raid_filter
B2: to retrieve info from lvmetad:
persistent_filter -> regex_filter -> usable_filter
This way, specifying the regex_filter in non-lvmetad case causes
the devices to be filtered based on regex first before processing
any other filters which can access disks (like md_component_filter).
This patch also streamlines the code for better readability.
Use refresh_filters instead of destroy_filters and init_filters
in refresh_toolcontext fn which deals with cmd->initialized.filters
correctly on refresh.
Make it possible to decide whether we want to initialize connections and
filters together with toolcontext creation.
Add "filters" and "connections" fields to struct
cmd_context_initialized_parts and set these in cmd_context.initialized
instance accordingly.
(For now, all create_toolcontext calls do initialize connections and
filters, we'll change that in subsequent patch appropriately.)
Move original lvmetad and lvmpolld initialization code from
_process_config fn to their own functions _init_lvmetad and
_init_lvmpolld (both covered with single _init_connections fn).
Add struct cmd_context_initialized_parts to wrap up information
about which cmd context pieces are initialized and add variable
of this struct type into struct cmd_context.
Also, move existing "config_initialized" variable that was directly
part of cmd_context into the new cmd_context.initialized wrapper.
We'll be adding more items into the struct cmd_context_initialized_parts
with subsequent patches...
Use find_config_tree_array for all config arrays. Also, add
INTERNAL_ERROR in case there should have been at least default
value defined for a setting but it was not returned for some
reason (either config_settings.h misconfiguration or other config
tree error printed by functions called by find_config_tree_array).
Before, we used general find_config_tree_node function to retrieve
array values. This had a downside where if the node was not found,
we had to insert default values directly in-situ after the
find_config_tree_node call. This way, we had two copies of default
values - one in config_settings.h and the other one directly in the
code where we found out that find_config_tree_node returned NULL and
hence we needed to fall back to defaults.
With separate find_config_tree_array used for array config values,
we keep all the defaults centrally in config_settings.h because
the new find_config_tree_array automatically returns these defaults
if it can't find any value set in the configuration.
This patch just makes the behaviour exactly the same for arrays as
for any other non-array type where we call find_config_tree_<type>
already, hence making the internal interface for handling array
values consistent with the rest of the config types.
Make it possible to define format for time that is displayed.
The way the format is defined is equal to the way that is used
for strftime function, although not all formatting options as
used in strftime are available for LVM2 - the set is restricted
(e.g. we do not allow newline to be printed). The lvm.conf
comments contain the whole list that LVM2 accepts for time format
together with brief description (copied from strftime man page).
For example:
(defaults used - the format is the same as used before this patch)
$ lvs -o+time vg/lvol0 vg/lvol1
LV VG Attr LSize Time
lvol0 vg -wi-a----- 4.00m 2015-06-25 16:18:34 +0200
lvol1 vg -wi-a----- 4.00m 2015-06-29 09:17:11 +0200
(using 'time_format = "@%s"' in lvm.conf - number of seconds
since the Epoch)
$ lvs -o+time vg/lvol0 vg/lvol1
LV VG Attr LSize Time
lvol0 vg -wi-a----- 4.00m @1435241914
lvol1 vg -wi-a----- 4.00m @1435562231
In log messages refer to it as system ID (not System ID).
Do not put quotes around the system_id string when printing.
On the command line use systemid.
In code, metadata, and config files use system_id.
In lvmsystemid refer to the concept/entity as system_id.
Move the lvm1 sys ID into vg->lvm1_system_id and reenable the #if 0
LVM1 code. Still display the new-style system ID in the same
reporting field, though, as only one can be set.
Add a format feature flag FMT_SYSTEM_ON_PVS for LVM1 and disallow
access to LVM1 VGs if a new-style system ID has been set.
Treat the new vg->system_id as const.
Allow cmd->unknown_system_id to be cleared during toolcontext
refresh.
Set a default value of "none" for global/system_id_source.
Allow local/system_id to be empty so it's not impossible for
a later config file to remove it.
In a file containing a system ID:
Any whitespace at the start of a line is ignored;
Blank lines are ignored;
Any characters after a # are ignored along with the #.
The system ID is obtained by processing the first line with
non-ignored characters.
If further lines with non-ignored characters follow, a warning is
issued.
Add WARNING messages if there are problems setting the requested
system ID.
Ban "localhost" as a prefix regardless of the system_id_source.
Use cmd->hostname instead of calling uname again.
Make system_id_source values case-insensitive (as with new settings like
log_debug_classes) and also accept machine-id to match the filename.
Require system ID to begin with an alphanumeric character.
Rename fn to make clear it's only validation for systemid
and always terminate result rather than imposing this on the caller.
In 2.02.99, _init_tags() inadvertently began to ignore the
dm_config_tree struct passed to it. "tags" sections are not
merged together, so the "tags" section in the main config file was
being processed repeatedly and other "tags" sections were ignored.
Just like MD filtering that detects components of software RAID (md),
add detection for firmware RAID.
We're not adding any native code to detect this - there are lots of
firmware RAIDs out there which is just out of LVM scope. However,
with current changes with which we're able to get device info from
external sources (e.g. external_device_info_source="udev"), we can
do this easily if the external device status source has this kind
of information - which is the case of "udev" source where the results
of blkid scans are stored.
This detection should cover all firmware RAIDs that blkid can detect and
which are identified as:
ID_FS_TYPE = {adaptec,ddf,hpt45x,hpt37x,isw,jmicron,lsi_mega,nvidia,promise_fasttrack,silicon_medley,via}_raid_member
Composite filter is a filter that can put several filters in one set.
This patch adds a switch when creating the composite filter which will
enable or disable external device info handles for all the filters
the composite filter encompasses.
We want to use this external device info for majority of the filters
which are in the "lvmetad filter chain" (or the respective part if
we're not using lvmetad).
Following patches will use the enabled external device handle in
concrete filters from the composite filter...
There are actually three filter chains if lvmetad is used:
- cmd->lvmetad_filter used when when scanning devices for lvmetad
- cmd->filter used when processing lvmetad responses
- cmd->full_fiilter (which is just cmd->lvmetad_filter + cmd->filter chained together) used
for remaining situations
This patch adds the third one - "cmd->full_filter" - currently this is
used if device processing does not fall into any of the groups before,
for example, devices which does not have the PV label yet and we're just
creating a new one or we're processing the devices where the list of the
devices (PVs) is not returned by lvmetad initially.
Currently, the cmd->full_filter is used exactly in these functions:
- lvmcache_label_scan
- _pvcreate_check
- pvcreate_vol
- lvmdiskscan
- pvscan
- _process_each_label
If lvmetad is used, then simply cmd->full_filter == cmd->filter because
cmd->lvmetad_filter is NULL in this case.
We need to use proper filter chain when we disable lvmetad use
explicitly in the code by calling lvmetad_set_active(0) while
overriding existing configuration. We need to reinitialize filters
in this case so proper filter chain is used. The same applies
for the other way round - when we enable lvmetad use explicitly in
the code (though this is not yet used).