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Drop very old original format of VDO target and focus on V2 version.
So some variables were renamed or replaced.
There is no compatibility preserved (with assumption so far this is
experimental feature and there is no real user).
Note - version currently VDO calls this version 6.2.
This is a followup patch to commit edb72cb70c
to support related lvm2 test suite tests.
A 'global/support_mirrored_mirror_log' bool configuration variable gets
introduced allowing the creation of, or conversion to mirrored 'mirror'
logs if set. The capability to create these in turn allows the rest of
the tests to perform activation of such existing LVs and their conversions
to disk/core 'mirror' logs.
Display a disclaimer warning if enabled that this is not for regular use.
Add definition of the enabled config option to respective test scripts.
Related: rhbz1643562
. When using default settings, this commit should change
nothing. The first PE continues to be placed at 1 MiB
resulting in a metadata area size of 1020 KiB (for
4K page sizes; slightly smaller for larger page sizes.)
. When default_data_alignment is disabled in lvm.conf,
align pe_start at 1 MiB, based on a default metadata area
size that adapts to the page size. Previously, disabling
this option would result in mda_size that was too small
for common use, and produced a 64 KiB aligned pe_start.
. Customized pe_start and mda_size values continue to be
set as before in lvm.conf and command line.
. Remove the configure option for setting default_data_alignment
at build time.
. Improve alignment related option descriptions.
. Add section about alignment to pvcreate man page.
Previously, DEFAULT_PVMETADATASIZE was 255 sectors.
However, the fact that the config setting named
"default_data_alignment" has a default value of 1 (MiB)
meant that DEFAULT_PVMETADATASIZE was having no effect.
The metadata area size is the space between the start of
the metadata area (page size offset from the start of the
device) and the first PE (1 MiB by default due to
default_data_alignment 1.) The result is a 1020 KiB metadata
area on machines with 4KiB page size (1024 KiB - 4 KiB),
and smaller on machines with larger page size.
If default_data_alignment was set to 0 (disabled), then
DEFAULT_PVMETADATASIZE 255 would take effect, and produce a
metadata area that was 188 KiB and pe_start of 192 KiB.
This was too small for common use.
This is fixed by making the default metadata area size a
computed value that matches the value produced by
default_data_alignment.
The pvscan systemd service for autoactivation was
mistakenly dropped along with the lvmetad related
services.
The activation generator program now looks at the new
lvm.conf setting "event_activation" (default 1) to
switch between event activation and direct activation.
Previously, the old use_lvmetad setting was used to
switch between event and direct activation.
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.
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.
The last commit related to this was incomplete:
"Implement lock-override options without locking type"
This is further reworking and reduction of the locking.[ch]
layer which handled all clustering, but is now only used
for file locking. The "locking types" that this layer
implemented were removed previously, leaving only the
standard file locking. (Some cluster-related artifacts
remain to be cleared out later.)
Command options to override or modify locking behavior
are reimplemented here without using the locking types.
Also, deprecated locking_type values are recognized,
and implemented as if one of the equivalent override
options was set.
Options that override file locking are:
. --nolocking disables all file locking.
. --readonly grants read lock requests without actually
taking a file lock, and refuses write lock requests.
. --ignorelockingfailure tries to set up file locks and
uses them normally if possible. When not possible, it
behaves like --readonly, but allows activation.
. --sysinit is the same as ignorelockingfailure.
. global/metadata_read_only acquires actual read file
locks, and refuses write lock requests.
(Some of these options could probably be deprecated
because they were added as workarounds to various
locking_type behaviors that are now deprecated.)
The locking_type setting now has one valid value: 1 which
refers to standard file locking. Configs that contain
deprecated values are recognized and still work in
largely the same way:
. 0 disabled all locking, now implemented like --nolocking
is set. Allow the nolocking option in all commands.
. 1 is the normal file locking setting and is unchanged.
. 2 was for external locking which was not used, and
reverts to normal file locking.
. 3 was for cluster/clvm. This reverts to normal file
locking, and prints messages about lvmlockd.
. 4 was equivalent to readonly, now implemented like
--readonly is set.
. 5 disabled all locking, now implemented like
--nolocking is set.
The device-mapper directory now holds a copy of libdm source. At
the moment this code is identical to libdm. Over time code will
migrate out to appropriate places (see doc/refactoring.txt).
The libdm directory still exists, and contains the source for the
libdevmapper shared library, which we will continue to ship (though
not neccessarily update).
All code using libdm should now use the version in device-mapper.
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/
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.
For reporting commands (pvs,vgs,lvs,pvdisplay,vgdisplay,lvdisplay)
we do not need to repeat the label scan of devices in vg_read if
they all had matching metadata in the initial label scan. The
data read by label scan can just be reused for the vg_read.
This cuts the amount of device i/o in half, from two reads of
each device to one. We have to be careful to avoid repairing
the VG if we've skipped rescanning. (The VG repair code is very
poor, and will be redone soon.)
Create a new dev->bcache_fd that the scanning code owns
and is in charge of opening/closing. This prevents other
parts of lvm code (which do various open/close) from
interfering with the bcache fd. A number of dev_open
and dev_close are removed from the reading path since
the read path now uses the bcache.
With that in place, open(O_EXCL) for pvcreate/pvremove
can then be fixed. That wouldn't work previously because
of other open fds.
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.
Callers that read larger amounts of data now get a pointer to read-only
data directly without copying it through an intermediate buffer. This
data is owned by the device layer so the callers no longer free it.
If it obtains the data, it passes it into the supplied callback function
and returns 1. Otherwise the callback receives failed = 1.
Updated config_file_read_fd to use this and similarly return the data
via a callback fn of its own.
Rename dev_read() to dev_read_buf() - the function that reads data
into a supplied buffer.
Introduce a new dev_read() that allocates the buffer it returns and
switch the important users over to this. No caller may change the
returned data. (For now, callers are responsible for freeing it after
use, but later the device layer will take full ownership.)
dev_read_buf() should only be used for tiny buffers or unimportant code
(such as the old disk formats).
The creation of wrapped around metadata - where the start of metadata is
written up to the end of the buffer and the remainder follows back at
the start of the buffer - is now restricted to cases where writing the
metadata in one piece wouldn't fit. This shouldn't happen in 'normal'
usage so let's begin treating the code for this as a special case that
can be ignored when optimising 'normal' cases.
Mark the first metadata area on each text format PV as MDA_PRIMARY.
Pass this information down to the device layer so that when
there are two metadata areas on a block device, we can easily
distinguish two independent streams of I/O.
Introduce enum dev_io_reason to categorise block device I/O
in debug messages so it's obvious what it is for.
DEV_IO_SIGNATURES /* Scanning device signatures */
DEV_IO_LABEL /* LVM PV disk label */
DEV_IO_MDA_HEADER /* Text format metadata area header */
DEV_IO_MDA_CONTENT /* Text format metadata area content */
DEV_IO_FMT1 /* Original LVM1 metadata format */
DEV_IO_POOL /* Pool metadata format */
DEV_IO_LV /* Content written to an LV */
DEV_IO_LOG /* Logging messages */
vgsplit shares the vg_rename code so that must only set the PV_MOVED_VG
flag introduced in commit 486ed10848
("vgmerge: Fix intermediate metadata corruption") on PVs that moved.
API for strtod() or strtoul() needs reset of errno, before it's being
called. So add missing resets in missing places and some also some
errno validation for out-of-range numbers.
Add new profilable configation setting to let user select
which metadata format of a created cache pool he wish to use.
By default the 'best' available format is autodetected at runtime,
but user may enforce format 1 or 2 ATM.
Code also detects availability for metadata2 supporting cache target.
In case of troubles user may easily Disable usage of this feature
by placing 'metadata2' into global/cache_disabled_features list.
User can specify metadata profile which stores important cache
geometry data for easy configuration.
Fix missing support for getting chunk_size, cache_mode, cache_policy
for a cache/cache pools volumes from configuration or metadata profile.
Basically code moving operation to have a single place resolving
thin_pool_chunk_size_policy.
Supported are generic & performance profiles.
Function is now shared between thin manipulation code and configuration
_CFG logic to obtain defaults and handle correct reporting upward coding
stack.
Because of contraints in renaming shifted rimage/rmeta LV names
the current RaidLV limit is a maximum of 10 SubLV pairs.
With the previous introduction of reshaping infratructure that
constriant got removed.
Kernel supports 253 since dm-raid target 1.9.0, older kernels 64.
Raise the maximum number of RaidLV rimage/rmeta pairs to 64.
If we want to raise past 64, we have to introdce a check for
the kernel supporting it in lvcreate/lvconvert.
Related: rhbz834579
Related: rhbz1191935
Related: rhbz1191978
In order to support striped raid5/6/10 LV reshaping (change
of LV type, stripesize or number of legs), this patch
introduces the changes to call the reshaping infratructure
from lv_raid_convert().
Changes:
- add reshaping calls from lv_raid_convert()
- add command definitons for reshaping to tools/command-lines.in
- fix raid_rimage_extents()
- add 2 new test scripts lvconvert-raid-reshape-linear_to_striped.sh
and lvconvert-raid-reshape-striped_to_linear.sh to test
the linear <-> striped multi-step conversions
- add lvconvert-raid-reshape.sh reshaping tests
- enhance lvconvert-raid-takeover.sh with new raid10 tests
Related: rhbz834579
Related: rhbz1191935
Related: rhbz1191978
When showing sizes with 'H|human' units we do use standard rounding.
This however is confusing users from time to time,
when the printed number uses some biger units i.e. GiB and there is just
tiny fraction of space missing.
So here is some real-life example with new 'r' unit.
$lvs
LV VG Attr LSize Pool Origin
lvol0 vg -wi-a----- 1.99g
lvol1 vg -wi-a----- <2.00g
lvol2 vg -wi-a----- <2.01g
Meaning is - lvol1 has 'slightly' less then 2.00g - from sign '<' user
can be aware the LV doesn't have full 2.00GiB in size so he
will be less surpriced allocation of 2G volume will not succeed.
$ vgs
VG #PV #LV #SN Attr VSize VFree
vg 2 2 0 wz--n- <6,00g <2,01g
For uses needing 'old' undecorated human unit simply will continue
to use 'H|h' units.
The new R|r may further change when we would recongnize some
other way how to improve readability.
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.
Introduce 'hard limit' for max number of cache chunks.
When cache target operates with too many chunks (>10e6).
When user is aware of related possible troubles he
may increase the limit in lvm.conf.
Also verbosely inform user about possible solution.
Code works for both lvcreate and lvconvert.
Lvconvert fully supports change of chunk_size when caching LV
(and validates for compatible settings).
Commit e947c362dd introduced
config_settings.h file for central place to store all definitions for
config options. By mistake, it used report/colums_as_rows instead
of report/columns_as_rows (missing "n" in "columns").
Enforce mirror/raid0/1/10/4/5/6 type specific maximum images when
creating LVs or converting them from mirror <-> raid1.
Document those maxima in the lvcreate/lvconvert man pages.
- resolves rhbz1366060
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.
Commit 3928c96a37 introduced
new defaults for raid number of stripes, which may cause
backwards compatibility issues with customer scripts.
Adding configurable option 'raid_stripe_all_devices' defaulting
to '0' (i.e. off = new behaviour) to select the old behaviour
of using all PVs in the VG or those provided on the command line.
In case any scripts rely on the old behaviour, just set
'raid_strip_all_devices = 1'.
- resolves rhbz1354650
lvm fullreport executes 5 subreports (vg, pv, lv, pvseg, seg) per each VG
(and so taking one VG lock each time) within one command which makes it
easier to produce full report about LVM entities.
Since all 5 subreports for a VG are done under a VG lock, the output is
more consistent mainly in cases where LVM entities may be changed in
parallel.
New report/output_format configuration sets the output format used
for all LVM commands globally. Currently, there are 2 formats
recognized:
- basic (the classical basic output with columns and rows, used by default)
- json (output is in json format)
This is a preparation for new CMDLOG report type which is going to be
used for reporting LVM command log.
The new report type introduces several new fields (log_seq_num, log_type,
log_context, log_object_type, log_object_group, log_object_id, object_name,
log_message, log_errno, log_ret_code) as well as new configuration settings
to set this report type (report/command_log_sort and report/command_log_cols
lvm.conf settings).
This patch also introduces internal report_cmdlog helper function
which is a wrapper over dm_report_object to report command log via
CMDLOG report type and which is going to be used throughout the code
to report the log items.
Wait to compare and choose alternate duplicate devices until
after all devices are scanned. During scanning, the first
duplicate dev is kept in lvmcache, and others are kept in a
new list (_found_duplicate_devs).
After all devices are scanned, compare all the duplicates
available for a given PVID and decide which is best.
If the dev used in lvmcache is changed, drop the old dev
from lvmcache entirely and rescan the replacement dev.
Previously the VG metadata from the old dev was kept in
lvmcache and only the dev was replaced.
A new config setting devices/allow_changes_with_duplicate_pvs
can be set to 0 which disallows modifying a VG or activating
LVs in it when the VG contains PVs with duplicate devices.
Set to 1 is the old behavior which allowed the VG to be
changed.
The logic for which of two devs is preferred has changed.
The primary goal is to choose a device that is currently
in use if the other isn't, e.g. by an active LV.
. prefer dev with fs mounted if the other doesn't, else
. prefer dev that is dm if the other isn't, else
. prefer dev in subsystem if the other isn't
If neither device is preferred by these rules, then don't
change devices in lvmcache, leaving the one that was found
first.
The previous logic for preferring a device was:
. prefer dev in subsystem if the other isn't, else
. prefer dev without holders if the other has holders, else
. prefer dev that is dm if the other isn't
Move checking the lvmetad state, and the possible rescan,
out of lvmetad_send() to the start of the command.
Previously, the token mismatch and rescan would occur
within lvmetad_send() for some other request. Now,
the token mismatch is detected earlier, so the
rescan can be done before the main command is in
progress. Rescanning deep within the processing of
another command will disturb the lvmcache state of
that other command.
A rescan already exists at the start of the command
for the case where foreign VGs are going to be read.
This same rescan is now also performed when there is
an lvmetad token mismatch (from a changed global_filter).
The commands pvscan/vgscan/lvscan/vgimport are excluded
from this preemptive checking/rescanning for lvmetad
because they want to do rescanning themselves explicitly.
If rescanning devices fails, then lvmetad has not been
correctly repopulated and should not be used, so make
the command revert to not using lvmetad.
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.
The metadata/record_lvs_history is global switch which enables or
disables recording historical LVs in metadata.
If both metadata/record_lvs_history=1 lvm.conf option and
--nohistory command switch is used at the same time, the
--nohistory prevails.
'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).
Normally, we generate and provide lvm.conf file where use_blkid_wiping
is set based on whether support for this is compiled in or not. This was
generated properly based on configure.
However, if lvm.conf is not used at all (someone deletes it) or the value
in lvm.conf is commented out (user edited it), we still need to use
proper default value that is based on DEFAULT_USE_BLKID_WIPING taken
from configure script - we used hardcoded value of "1" in this case
by mistake.
Just for convenience to display all new configuration settings
introduced since given version (before, there was only --atversion
to display settings introduced in concrete version).
For example:
$ lvmconfig --type new --sinceversion 2.2.120
allocation {
# cache_mode="writethrough"
# cache_settings {
# }
}
global {
use_lvmlockd=0
# lvmlockd_lock_retries=3
# sanlock_lv_extend=256
use_lvmpolld=1
}
activation {
}
# report {
# compact_output_cols=""
# time_format="%Y-%m-%d %T %z"
# }
local {
# host_id=0
}
Here Coverity cannot see the pointer cannot be NULL in this
code path - opened coverity case #00531860.
We could make a model to avoid seeing related reports,
but then we loose coverage for modeled function.
So decided to add minor hint for this case.
The new report/compact_output_cols setting has exactly the same effect
as report/compact_output setting. The difference is that with the new
setting it's possible to define which cols should be compacted exactly
in contrast to all cols in case of report/compact_output.
In case both compact_output and compact_output_cols is enabled/set,
the compact_output prevails.
For example:
$ lvmconfig --type full report/compact_output report/compact_output_cols
compact_output=0
compact_output_cols=""
$ lvs vg
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
lvol0 vg -wi-a----- 4.00m
---
$ lvmconfig --type full report/compact_output report/compact_output_cols
compact_output=0
compact_output_cols="data_percent,metadata_percent,pool_lv,move_pv,origin"
$ lvs vg
LV VG Attr LSize Log Cpy%Sync Convert
lvol0 vg -wi-a----- 4.00m
---
$ lvmconfig --type full report/compact_output report/compact_output_cols
compact_output=1
compact_output_cols="data_percent,metadata_percent,pool_lv,move_pv,origin"
$ lvs vg
LV VG Attr LSize
lvol0 vg -wi-a----- 4.00m
This mainly makes the description text use 80 columns.
There are a few minor adjustments to wording to help
the text layout, and a couple minor improvements to
descriptions.
Before printing a commented automatic config value,
print a line describing what it is. Otherwise, the
commented value can look like it's a part of an
example preceding it.
Move code which runtime detects settings for cache_policy
out of config dir to cache seg handling code.
Also mark cache_mode as command profilable setting.
As cache_policy is evaluated in runtime, we no longer should use
CFG_COMMENTED, but have to switch to CFG_UNDEFINED.
So as long as the value is undefined, it's runtime evaluated.
Once it's set - it's always respected (no runtime fallback).
Also fix version of introduced settings to 2.2.128.
Add code to detect available cache features.
Support policy_mq & policy_smq features which might be disabled.
Introduce global_cache_disabled_features_CFG.
Add new profilable configurables:
allocation/cache_policy
allocation/cache_settings
and mark allocation/cache_pool_chunk_size as profilable as well.
Obsolete allocation/cache_pool_cachemode and
introduce new allocation/cache_mode instead.
Rename DEFAULT_CACHE_POOL_POLICY to DEFAULT_CACHE_POLICY.
The CFG_SECTION_NO_CHECK flag can be used to mark a section
and its whole subtree as containing settings where checks
won't be made (lvmconfig --validate).
These are setting where we don't know the names and and type
in advance and they're recognized in runtime. As we don't know
the type and name in advance, we can't do any checks here
of course.
Use this flag with great care as it disables config checks
for the whole config subtree found under such section.
This flag is going to be used by subsequent patches from
Zdenek to support some cache settings...
Commit 7e728fe1a1 added a log call
directly in find_config_tree_array when defaults are used.
This patch also adds the log for the value which is found in
existing configuration and for which defaults are not used.
For example:
Defaults used:
config/config.c:1428 devices/scan not found in config: defaulting to scan = [ "/dev" ]
Value defined in configuration used:
config/config.c:1431 Setting devices/scan to scan = [ "/dev", "/mydev", "/abc" ]
This makes the logging consistent with the other find_config_tree_* functions.
Require global/{thin,cache}_{check,repair}_options to be always defined.
If not defined directly by user in the configuration and if there's no
concrete default option to use, make "" (empty string) the default one -
it's then clearly visible in the "lvmconfig --type default" (and
generated lvm.conf) and also it makes its handling in the code more
straightforward so we don't need to handle undefined values.
This means, if there are no default values for these settings defined,
we end up with this generated now:
{thin,cache}_{check,repair}_options = [ "" ]
So the value is never undefined and if it is, it's an error.
(The cache_repair_options is actually not used in the code at the moment,
but once the code using this setting is in, it will follow the same logic
as used for thin_repair_options.)
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.
including the allow_override_lock_modes setting.
It was not possible to override default lock modes any longer,
since the command line options had already been removed.
A mechanism will probably be required later that puts part of
this back.
Just like we have DEFAULT_USE_LVMETAD (or DEFUALT_USE_LVMPOLLD), use
fallback_to_lvm1=1 lvm.conf setting if we configured lvm2 with
--enable-lvm1-fallback and use fallback_to_lvm1=0 otherwise.
Also, generate proper lvm.conf.in with unconfigured value.
