IF YOU WOULD LIKE TO GET AN ACCOUNT, please write an
email to Administrator. User accounts are meant only to access repo
and report issues and/or generate pull requests.
This is a purpose-specific Git hosting for
BaseALT
projects. Thank you for your understanding!
Только зарегистрированные пользователи имеют доступ к сервису!
Для получения аккаунта, обратитесь к администратору.
Add code to handle creation of thin-pool with VDO data backend
which can be seen as compressed deduplicated thin-pool.
To avoid need of changing to many internal APIs, pass the conversion
parameters for create thin-pool data volume via cmd_context.
Introduce struct vdo_convert_params {} to pass-in all the parameters
needed for the conversion of an LV to a vdopool + vdo LV.
Function convert_vdo_lv() is also able to create a new LV and swap
segments, so the passed in LV can be later on use for futher
conversion so this refactoring makes it ready for more enhanced
usage.
Introduce vdo_convert_params and use vdo_params from this structure
also with lvcreate_params.
Later we will use this for convertion of thin-pool data volume to VDO.
If a RaidLV mapping is required to be refreshed as a result of temporarily failed
and recurred RAID leg device (pairs) caused by writes to the LV during failure,
the requirement is reported by volume health character r' in position 9 of the
LV's attribute field (see 'man lvs' about additional volume health characters).
As this character can be overlooked, this patch adds messages to the top
of the lvs command output informing the user explicitely about the fact.
Fix typos in previous commit 3589e515d.
Both commands default [raid_](min|max)recoveryrate to 0 but ensure
min_recovery_rate is not larger than max_recoveryrate. This results
in command failure without requesting the user to also define
max_recovery_rate >= min_recovery_rate.
Fix both commands by defining max_recovery_rate = min_recoveryrate
in case "lvcreate/lvchange --minrecoveryrate Size ..." requests a
larger value than current maxrecoveryrate without also giving option
Both commands default [raid_](min|max)recoveryrate to 0 but ensure
min_recovery_rate is not larger than max_recoveryrate. This results
in command failure without requestinng the user to also define
max_recovery_rate >= min_recovery_rate.
Fix both commands by defining max_recovery_rate = min_recoveryrate
in case "lvcreate/lvchange --minrecoveryrate Size ..." requests a
larger value than current maxrecoveryrate without also giving option
"--maxrecoveryrate Size ..." with a size greater or equal than min.
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.)
A pvid string read from system.devices could be less
then ID_LEN since system.devices fields can be edited.
Ensure the pvid buffer is ID_LEN+1 even if the string
read from the file is shorter.
- add new comparison between old and new entries, and use this
as the basis for new dedicated output for check and update
- add new --refresh option to search for missing PVIDs on all
devices, and possibly update the device ID
- internally, only use the term "refresh" for cases where a
new device ID may be found and assigned for a missing PVID
Since LVM 2.02 it appears that compiling LVM on a platform which
lacks a shared library linker/loader will fail to produce any
binaries (dmsetup, lvm2, etc).
Adds support for the standard --disable-shared flag, and
use it to disable attempts at building shared libraries.
Modified-by: zkabelac
Fix some interactions between device IDs and hints. Hints
may limit the scanned devices which should not always trigger
a search for the PVs that were intentionally not scanned.
Hints should also be invalidated if they contain a device
that's become excluded by an internal filter such as the
device_id filter.
Fix commit 847f1dd99c
"device_id: rewrite validation of devname entries"
which began calling device_ids_refresh() in cases where it
was unnecessary, leading to extra PV searches and warnings.
Specifically, a command like "lvs <vg>" would use the hints
file to scan only devices for the named VG. This means that
scanning other PVs would be skipped, and device IDs of those
PVs could not be validated because there are no PVID values
to verify. This missing info would cause messages about
the missing info, and would cause device_ids_refresh to
search for the PVs that had been intentionally skipped.
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.
Make a local copy of the 'idx' string to avoid
overlapping during the rebuild of name.
This fixes cases where users specified raid
component LVs for moving.
Reported-by: kotarou3@github.com
When creating thin pool or check pool there is allocated LV
for metadata and for such allocation user should be able to
specify list of PVs on cmdline.
Also fix unused passed list of PV for thick to thin conversion,
where the code was using whole PV set from a VG (but since it's
been not enabled on cmdline, user could not hit this issue).
Also remove unneeded initialization of use_pvh.
Reuse existing report/headings config setting to make it possible to
change the type of headings to display:
0 - no headings
1 - column name abbreviations (default and original functionality)
2 - full column names (column names are equal to exact names that
-o|--options also accepts to set report output)
Also, add '--headings none|abbrev|full|0|1|2' command line option
so we are able to select the heading type for each LVM reporting
command directly.
Set the lock_args string in addition to doing initialization.
lvconvert calls lockd_init_lv_args() directly, skipping
the normal lockd_init_lv() which usually sets lock_args.
lvmlockd locking for swapmetadata adjusted for commit
ac36153e99 lvconvert: preserve UUID for swapped metadata
Now that the LV uuid is swapped between LVs, the lvmlockd lock can
simply be moved between them, and the same lock can continue to be
used for the LV outside of the pool.
Once lvm2 repairs pool's metadata LV and preserves the original metadata LV
with unmodified metadata, for such LV in VG use newly created UUID for new
_pmspare and actually preserve UUID for this hidden _pmspare (if it
exists).
The lockd lock needs to be freed for the LV that is becoming
the new metadata LV, and a new lockd lock needs to be created
for the old metadata LV that is becoming an independent LV.
Fixes b3e45219c2
Use cachepool name for create name for metadata backup LV.
(so we do not generate 2 'sequences' of metadata filenames.)
Move path preparion before handling _pmspare.
Also drop extra call to sync_local_dev_names() as it's
already got in sync with call of exec_cmd().
When repair thinpool or cachepool, lvm2 leaves original metadata
volume backup. To avoid potential damage of those data, mark such
volume as 'read-only' and also allow user to use --setactivationskip
option for this volume.
TODO: likely better default would be to automatically skip, but
that might need some more thinking about recovery reporting doc.
Replace the use of internal /dev/mapper names with the use of
public LV names /dev/vg/lv for use with repair tools.
For this make the activation of _pmspare LV to be handled as
a component activation with public name.
Metadata is already atomatically activated this way (as readonly).
So if there is any 'error' happening, we leave public LVs in
system.
lvresize --usepolicy requires resized LVs to be active.
(So it's not only required for shared VG).
The test for active pool needs to use lv_info to query 'layer'
otherwise the pool is considered inactive if it was not activated
explicitely - thun 'implicit' activation with VDO or ThinLV was
not managed by --usepolicy option.
Update pool conversion function to handle also conversion of
thick LV to thin LV by moving thick LV into thin pool data LV
and creating fully provissioned thin LV on top of this volume.
Reworking existing conversion to use insert_layer_for_lv co
the uuid is now kept with thin-pool - this should however not
really matter as we are doing full deactivation & activation cycle.
With conversion to thin LV user can use same set of arguments
to set chunk-size.
TODO: add some smart code to decide best values for chunks sizes.
For proper functionality of insert_layer_for_lv we need to
move more bits to layerd LV.
Add some missing new types and correct usage of caller,
so the new LV type is set after the movement.
Validate cache origin in front of the prompt.
Also add some rules to command description file.
TODO:
more validation needed also for lvcreate,
more complex rules with "OR" seems to be needed.
Enable support to cache thin/error/zero virtual targets.
Use can now select whether he want to cache whole thin-pool,
or an individual thin volume out of whole thin-pool.
Support using zero and error LVs as data volume for
cachepool is possibly useful for benchmarking, not much
can be expected from such setup.
This vdo parameter existed in the early stage of integration of vdo into lvm2,
but later it's been removed from vdoformat tool - so actually if
there would be any non-zero value it would cause error on lvcreate.
Option was not stored on disk in lvm2 metadata.
Remove this vdo parameter from lvm2 sources.
(Although this vdo parameter will be still accepted on cmdline through
--vdosettings option, but it will be ignored.)
The command "lvcreate --type thin --snapshot ..." to create a thin
snapshot would fail.
commit d651b340e6 removed the optional
"--type thin" from the command definition "lvcreate --snapshot LV_thin",
and added --type thin as AUTOTYPE. This was correct and should not have
changed anything if all the command defs were correct, but it broke
the "lvcreate --type thin --snapshot" case. It reveals a problem in a
different command definintion: "lvcreate --type thin LV_thin" that was
missing --snapshot in its OO list.
If we are executing 'report_for_selection' to do an internal report
just for the selection itself (not for display), we can call it more
than once. In that case, we are reusing the same selection handle
(e.g. inside 'process_each_lv_in_vg').
The selection handle has 'report_type' field which is a union of all
report types needed for the report based on selection fields we actually
use.
The 'report_type' is further clarified based on checks and rules inside
'_get_final_report_type' which 'report_for_selection' calls. Then, this
final report type unambiguously identifies proper branch to take in
'report_all_in_{pv,vg,lv}' that is called next.
If the 'report_for_selection' is called more than once with the same
selection handle, we need to make sure that we always restore the report
type to its initial value, so all the rules inside 'report_for_selection'
are applied correctly next time.
This patch fixes the missing restoration of the 'report_type' value in
'selection_handle' that is reused for recurring 'report_for_selection'
calls.
An example scenario where this failed was with selecting an LV for
removal with "lvremove --select" while using a field in the selection
that required extra DM info or DM status call for the LV (that is,
"Logical Volume Device Info Fields" and "Logical Volume Device Status Fields"
as visible in 'lvs -S help').
vgrename does not support -S|--select, so do not provide a hint about
using it. Instead, provide a hint about using VG uuid directly.
❯ vgs
WARNING: VG name vg1 is used by VGs DXjcSK-gWfu-5gLh-9Kbg-sG49-dtRr-GqXzGL and MVMfyM-sjOa-M2xV-AT4Y-JddR-h4SP-UO5Ttk.
Fix duplicate VG names with vgrename uuid, a device filter, or system IDs.
VG #PV #LV #SN Attr VSize VFree
vg1 1 0 0 wz--n- 124.00m 124.00m
vg1 1 0 0 wz--n- 124.00m 124.00m
(vgrename does not support -S|--select)
❯ vgrename vg1 vg2
WARNING: VG name vg1 is used by VGs DXjcSK-gWfu-5gLh-9Kbg-sG49-dtRr-GqXzGL and MVMfyM-sjOa-M2xV-AT4Y-JddR-h4SP-UO5Ttk.
Fix duplicate VG names with vgrename uuid, a device filter, or system IDs.
Multiple VGs found with the same name: skipping vg1
Use VG uuid in place of the VG name.
(vgchange does support -S|--select)
❯ vgchange --addtag a vg1
WARNING: VG name vg1 is used by VGs DXjcSK-gWfu-5gLh-9Kbg-sG49-dtRr-GqXzGL and MVMfyM-sjOa-M2xV-AT4Y-JddR-h4SP-UO5Ttk.
Fix duplicate VG names with vgrename uuid, a device filter, or system IDs.
Multiple VGs found with the same name: skipping vg1
Use --select vg_uuid=<uuid> in place of the VG name.
When we are using -S|--select for non-reporting tools while using command log
reporting (log/report_command_log=1 setting), we need to create an internal
processing handle to handle the selection itself. In this case, the internal
processing handle to execute the selection (to process the -S|--select) has
a parent handle (that is processing the actual non-reporting command).
When this parent handle exists, we can't destroy the command log report
in destroy_processing_handle as there's still the parent processing to
finish. The parent processing may still generate logs which need to be
reported in the command log report. If the command log report was
destroyed prematurely together with destroying the internal processing
handle for -S|--select, then any subsequent log request from processing
the actual command (and hence an attermpt to access the command log report)
ended up with a segfault.
See also: https://bugzilla.redhat.com/show_bug.cgi?id=2175220
There may be some unconventional methods of sharing disks with vgimport
where hints could cause confusion. Hints should be disabled when
sharing disks, or pvscan --cache used to regenerate hints as needed,
but invalidating hints from vgimport might help reduce confusion.
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.
Addressing problem for user of system without default bash shell.
As reported "set -o pipefail" is a bashism that causes the build to
fail when /bin/sh does not point to bash.
For example, this has been observed causing build failures
on Gentoo when /bin/sh is symlinked to /bin/dash.
Rule has been reworked and we started to use .DELETE_ON_ERROR to
ensure that with any errors during file generation, such invalid
file is automatically removed.
Rules were reworked to avoid using pipe and instead use temporary
files when necessary.
Printing lines with echo was replaced with POSIX recomended 'printf'
as proposed by reporter since handling of escape characters and
the "-n" flag for "echo" aren't portable across shells.
Also some build deps has been added.
Bug: https://bugzilla.redhat.com/show_bug.cgi?id=1822280
Gentoo-bug: https://bugs.gentoo.org/682404
Gentoo-bug: https://bugs.gentoo.org/716496
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1822280
Reported-by: Michael Orlitzky <michael@orlitzky.com>
TODO: investage if the temporary files could be handled via some
intermediate target solution - ATM I couldn't make it work equally
well as current solution use shell 'trap' to remove temp file.
Commit dropping lvmetad support 117160b27e
also removed cleaning of its generated files. However we need to keep
this functionality, otherwise we can leak them during various bisect.
Easier is to keep such rules forever.
Also commit c1ab9fb37f moved cmds.h to
include, so again keep it removed so it's not left there and in any
case could not misslead anyone.
Use configure detection instead of trying to directly include
blkid.h inside lvresize.c - where we do not pass in BLKID_CFLAGS
and since we actually do not need to use blkid there, introeduce
test variable HAVE_BLKID_SUBLKS_FSINFO and avoid trying to
use blkid.h in this place - this also fixes builing problem for
systems without blkid.h.
Fix hang of vgimportclone command when:
the PV(s) being imported are not actually clones/duplicates, and
the -n vgname arg is the same as the current vgname.
(Not the intended use of the command, but it should still work.)
In this case, the old and new vgnames ended up being the same, when
the code expected they would be different. A file lock on both the
old and new vgnames is used, so when both flocks are on the same
file, the second blocks indefinitely.
Fix the new vgname to be the old name plus a numeric suffix, which
is the expected result.
When refreshing all LVs in a VG, skip processing of thick snapshots,
since they will be refreshed through its origin LV.
Should reduce some unnecessary ioctl().
"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>.
Enhance checking vdo constains so it also handles changes of active VDO LVs
where only added difference is considered now.
For this also the reported informational message about used memory
was improved to only list consuming RAM blocks.
If one of the PVs in the VG does not hold metadata, then the
command would fail, thinking that PV was from a different VG.
Also add missing free on that error path.
Handle multiple devices using the same serial number as
their device id. After matching devices to devices file
entries, if there is a discrepency between the ondisk PVID
and the devices file PVID, then rematch devices to
devices file entries using PVID, looking at all disks
on the system with the same serial number.
When executing process_each_lv_in_vg, we process live LVs first and
after that, we process any historical LVs. In case we have just removed
an LV, which also means we have just made it "historical" and so it
appears as fresh item in vg->historical_lvs list, we have to skip it
when we get to processing historical LVs inside the same process_each_lv_in_vg
call.
The simplest approach here, without introducing another LV list, is to
simply mark such historical LVs as "fresh" directly in struct
historical_logical_volume when we have just removed the original LV
and created the historical LV for it. Then, we just need to check the
flag when processing historical LVs and skip it if it is "fresh".
When we read historical LVs out of metadata, they are marked as
"not fresh" and so they can be processed as usual.
This was mainly an issue in conjuction with -S|--select use:
# lvmconfig --type diff
metadata {
record_lvs_history=1
}
(In this example, a thin pool with lvol1 thin LV and lvol2 and lvol3 snapshots.)
# lvs -H vg -o name,pool_lv,full_ancestors,full_descendants
LV Pool FAncestors FDescendants
lvol1 pool lvol2,lvol3
lvol2 pool lvol1 lvol3
lvol3 pool lvol2,lvol1
pool
# lvremove -S 'name=lvol2'
Logical volume "lvol2" successfully removed.
Historical logical volume "lvol2" successfully removed.
...here, the historical LV lvol2 should not have been removed because
we have just removed its original non-historical lvol2 and the fresh
historical lvol2 must not be included in the same processing spree.
Exclude the new fs resizing capabilities at build time
(rather than run time) if the necessary libblkid features
are not available. When excluded, all fs resizing options
are translated to resize_fsadm. Accessing the new
features now requires rebuilding lvm if libblkid is
upgraded.
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.
The new option "--fs String" for lvresize/lvreduce/lvextend
controls the handling of file systems before/after resizing
the LV. --resizefs is the same as --fs resize.
The new option "--fsmode String" can be used to control
mounting and unmounting of the fs during resizing.
Possible --fs values:
checksize
Only applies to reducing size; does nothing for extend.
Check the fs size and reduce the LV if the fs is not using
the affected space, i.e. the fs does not need to be shrunk.
Fail the command without reducing the fs or LV if the fs is
using the affected space.
resize
Resize the fs using the fs-specific resize command.
This may include mounting, unmounting, or running fsck.
See --fsmode to control mounting behavior, and --nofsck to
disable fsck.
resize_fsadm
Use the old method of calling fsadm to handle the fs
(deprecated.) Warning: this option does not prevent lvreduce
from destroying file systems that are unmounted (or mounted
if prompts are skipped.)
ignore
Resize the LV without checking for or handling a file system.
Warning: using ignore when reducing the LV size may destroy the
file system.
Possible --fsmode values:
manage
Mount or unmount the fs as needed to resize the fs,
and attempt to restore the original mount state at the end.
nochange
Do not mount or unmount the fs. If mounting or unmounting
is required to resize the fs, then do not resize the fs or
the LV and fail the command.
offline
Unmount the fs if it is mounted, and resize the fs while it
is unmounted. If mounting is required to resize the fs,
then do not resize the fs or the LV and fail the command.
Notes on lvreduce:
When no --fs or --resizefs option is specified:
. lvextend default behavior is fs ignore.
. lvreduce default behavior is fs checksize
(includes activating the LV.)
With the exception of --fs resize_fsadm|ignore, lvreduce requires
the recent libblkid fields FSLASTBLOCK and FSBLOCKSIZE.
FSLASTBLOCK*FSBLOCKSIZE is the last byte used by the fs on the LV,
which determines if reducing the fs is necessary.
Take the devices file lock before creating a new devices file.
(Was missed by the change to preemptively create the devices
file prior to setup_devices(), which was done to improve the
error path.)
When using --all, if one VG is skipped, continue adding
other VGs, and do not return an error from the command
if some VGs are added. (A VG is skipped if it's missing PVs.)
If the command fails during devices file setup or device
scanning, then remove the devices file if it has been
newly created by the command, and exit with an error.
If devices from a named VG are not imported (e.g. the
VG is missing devices), then remove the devices file if
it has been newly created by the command, and exit with
an error.
If --all VGs are being imported, and no devices are found
to include in the devices file, then remove the devices
file if it has been newly created by the command, and
exit with an error.
Names matching internal code layout.
Functionc in thin_manip.c uses thin_pool in its name.
Keep 'pool' only for function working for both cache and thin pools.
No change of functionality.
Certain args can't be used in lvm shell ("interactive mode") because
they are not supported there. Add ARG_NONINTERACTIVE flag to mark
such args and error out if we're in interactive mode and at the same
time we detect use of such argument.
Currently, this is the case for --reportformat arg - we don't support
changing the format per command in lvm shell. The whole shell is running
under a reportformat chosen at shell's start.
If we failed or logged anything before we actually execute given command
in lvm shell, we couldn't report the log using lastlog command after.
This patch adds specific 'pre-cmd' log report object type to identify
such log messages and enables lastlog to report even this log.
The new --valuesonly option causes the lvmconfig output to contain only
values without keys for each config node. This is practical mainly in
case where we use lvmconfig in scripts and we want to assign the value
to a different custom key or simply output the value itself without the
key.
For example:
# lvmconfig --type full activation/raid_fault_policy
raid_fault_policy="warn"
# lvmconfig --type full activation/raid_fault_policy --valuesonly
"warn"
# my_var=$(lvmconfig --type full activation/raid_fault_policy --valuesonly)
# echo $my_var
"warn"
Internally, NUM and BIN fields are marked as DM_REPORT_FIELD_TYPE_NUM_NUMBER
through libdevmapper API. The new 'json_std' format mandates that the report
string representing such a value must be a number, not an arbitrary string.
This is because numeric values in 'json_std' format do not have double quotes
around them. This practically means, we can't use string synonyms
("named reserved values") for such values and the report string must always
represent a proper number.
With 'json' and 'basic' formats, this is not an issue because 'basic' format
doesn't have any structure or typing at all and 'json' format puts all values
in quotes, including numeric ones.
If using JSON format for lvm shell's output, the error message about
exceeding the maximum number of arguments was not reported on output if
this condition was ever hit.
This is because the JSON format (as well as any other future format)
requires extra formatting compared to "basic" format and so it also
requires extra calls when it comes to reporting. The report needs to
be added to a report group and then popped and put on output with
specialized "dm_report_group_output_and_pop_all".
This "output and pop" is normally executed after we execute the command
in the lvm shell. When we didn't get to the command exection at all because
some precondition was not met (like hitting the limit for the number of
arguments for the command here), we skipped this important call and
so there was no log report output.
Right now, it's only this exact error message for which we need to call
"output and pop" directly, all the other error messages are about
initializing and setting the log report itself which we can't report
obviously.
Before this patch:
lvm> pvs 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
lvm>
With this patch applied:
lvm> pvs 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
{
"log": [
{"log_seq_num":"1", "log_type":"error", "log_context":"shell", "log_object_type":"cmd", "log_object_name":"", "log_object_id":"", "log_object_group":"", "log_object_group_id":"", "log_message":"Too many arguments, sorry.", "log_errno":"-1", "log_ret_code":"0"}
]
}
If there's any other error message in the future before we execute the
command itself, we also need to call the "output and pop" directly.
When creating VDO pool based of % values, lvm2 is now more clever
and avoids to create 'unsupportable' sizes of physical backend
volumes as 16TiB is maximum size supported by VDO target
(and also limited by maximum supportable slabs (8192) based on slab
size.
If the requested virtual size is approaching max supported size 4PiB,
switch header size to 0.
Add function to check for avaialble memory for particular VDO
configuration - to avoid unnecessary machine swapping for configs
that will not fit into memory (possibly in locked section).
Formula tries to estimate RAM size machine can use also with
swapping for kernel target - but still leaving some amount of
usable RAM.
Estimation is based on documented RAM usage of VDO target.
If the /proc/meminfo would be theoretically unavailable, try to use
'sysinfo()' function, however this is giving only free RAM without
the knowledge about how much RAM could be eventually swapped.
TODO: move _get_memory_info() into generic lvm2 API function used
by other targets with non-trivial memory requirements.
