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Commit 813347cf84 added extra validation,
however in this particular we do want to trim suffix out so rather ignore
resulting error code here intentionaly.
If a single, standard LV is specified as the cache, use
it directly instead of converting it into a cache-pool
object with two separate LVs (for data and metadata).
With a single LV as the cache, lvm will use blocks at the
beginning for metadata, and the rest for data. Separate
dm linear devices are set up to point at the metadata and
data areas of the LV. These dm devs are given to the
dm-cache target to use.
The single LV cache cannot be resized without recreating it.
If the --poolmetadata option is used to specify an LV for
metadata, then a cache pool will be created (with separate
LVs for data and metadata.)
Usage:
$ lvcreate -n main -L 128M vg /dev/loop0
$ lvcreate -n fast -L 64M vg /dev/loop1
$ lvs -a vg
LV VG Attr LSize Type Devices
main vg -wi-a----- 128.00m linear /dev/loop0(0)
fast vg -wi-a----- 64.00m linear /dev/loop1(0)
$ lvconvert --type cache --cachepool fast vg/main
$ lvs -a vg
LV VG Attr LSize Origin Pool Type Devices
[fast] vg Cwi---C--- 64.00m linear /dev/loop1(0)
main vg Cwi---C--- 128.00m [main_corig] [fast] cache main_corig(0)
[main_corig] vg owi---C--- 128.00m linear /dev/loop0(0)
$ lvchange -ay vg/main
$ dmsetup ls
vg-fast_cdata (253:4)
vg-fast_cmeta (253:5)
vg-main_corig (253:6)
vg-main (253:24)
vg-fast (253:3)
$ dmsetup table
vg-fast_cdata: 0 98304 linear 253:3 32768
vg-fast_cmeta: 0 32768 linear 253:3 0
vg-main_corig: 0 262144 linear 7:0 2048
vg-main: 0 262144 cache 253:5 253:4 253:6 128 2 metadata2 writethrough mq 0
vg-fast: 0 131072 linear 7:1 2048
$ lvchange -an vg/min
$ lvconvert --splitcache vg/main
$ lvs -a vg
LV VG Attr LSize Type Devices
fast vg -wi------- 64.00m linear /dev/loop1(0)
main vg -wi------- 128.00m linear /dev/loop0(0)
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.
When pvmoving LV - the target for LV is a mirror so the validation
that checked the type is matching was incorrect.
While we need a more generic enhancment of LVS output for pvmoved LVs,
for now at least stop showing internal errors and 'X' symbols in attrs.
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/
If the tools for checking thin_pool or cache metadata are missing,
issue rather just a WARNING, but let the operation of activation
continue.
This has the advantage, the if user is missing those tools,
but he already started to use thinpool or cacheing, he can
access these volumes with a WARNING.
Also if the user is using too old tools i.e. for CacheV2 format
dmpd tool 0.7 is required - provide informative WARNING and
skip failure from older tool version which can't understand
new format V2.
Just like lvm2 has internal devices like _tdata which is using UUID with
suffix, there is similar private type of device for crypto device where
they are using CRYPT-TEMP uuid prefix.
Also ignore stratis.
Some kernel version suffer from bad state transition where a device
steps into 'frozen' mode. Any application that tries to read such
raid gets unfortunatelly bloked.
As some sort of protection try to skip such raid device from being
scanned to minimize chances to block lvm2 command on such scan.
When such device is found, warning gets printed.
RaidLVs on read_only_volume_list have their SubLVs
activated readonly thus disabling metadata updates
or image resynchronization/recovery. Bug also causes
automatic repairs to fail.
Fix by always activating the RAID SubLVs readwrite.
Resolves: rhbz1208269
When snapshot is created in read-only mode with 'lvcreate -s -pr...',
lvm2 still needs to be able to write to layered -cow volume
to store metadata and exceptions blocks.
TODO: in some case we might be able to do full tree with read-only
volume but this probably needs futher validation:
1. checking snapshot header already exist
2. origin & snapshot are both in read-only mode.
Introduce:
lv_is_component() check is LV is actually a component device.
lv_component_is_active() checking if any component device is active.
lv_holder_is_active() is any component holding device is active.
Use new 3rd. state of trace_pvmove_deps == 2.
In this state we know, we have already seen the node and can skip futher
testing. Remainging value 1 signals we want to track, and value 0
is for ignoring tracking, but node is still checking in this case.
Reduces large amount of duplicate ioctl queries.
Use code which detectes handlers in a way, which is more
backward-compatible friendly.
Replace read of 'sysfs' uuid entry with dm ioctl call.
Use /sys/block/dm-X/holders path instead of
new path /sys/dev/block/major:minor/holders.
TODO:
There are few more occurencies of this logic around the code
so some abstract interface should be considered.
When pvmove is finished and does 'suspend/resume' on PVMOVE LV,
on resume path committed metadata are already showing 'standalone'
pvmove LV prepared just for removal.
However code should be able to 'resume' preloaded LV there were
participating in pvmove operation.
Previously this was all done in the 'tools' part of lvm2 code.
So the lvconvert upon pvmove finish had to explicitely call 'resume' on every such LV.
Now 'smarted' activation code is able to deduce and combine all information from
the active dm table and committed metadata so single call resolves
it all in one go.
Internally holders are detected by reading sysfs directory to capture
all needed UUID which are then looked in lvm2 metadata and all such
LVs are automatically collected into dmtree.
When metadata LV size was over DM_THIN_MAX_METADATA_SIZE sectors,
the info() routine was incorrectly trying to match bigger size,
while we do never pass any bigger device.
Fixing a case, where lvs should be displaying status for metadata
LV with 16GB size.
In order to support striped raid5/6/10 LV reshaping (change
of LV type, stripesize or number of legs), this patch
introduces infrastructure prerequisites to be used
by raid_manip.c extensions in followup patches.
This base is needed for allocation of out-of-place
reshape space required by the MD raid personalities to
avoid writing over data in-place when reading off the
current RAID layout or number of legs and writing out
the new layout or to a different number of legs
(i.e. restripe)
Changes:
- add members reshape_len to 'struct lv_segment' to store
out-of-place reshape length per component rimage
- add member data_copies to struct lv_segment
to support more than 2 raid10 data copies
- make alloc_lv_segment() aware of both reshape_len and data_copies
- adjust all alloc_lv_segment() callers to the new API
- add functions to retrieve the current data offset (needed for
out-of-place reshaping space allocation) and the devices count
from the kernel
- make libdm deptree code aware of reshape_len
- add LV flags for disk add/remove reshaping
- support import/export of the new 'struct lv_segment' members
- enhance lv_extend/_lv_reduce to cope with reshape_len
- add seg_is_*/segtype_is_* macros related to reshaping
- add target version check for reshaping
- grow rebuilds/writemostly bitmaps to 246 bit to support kernel maximal
- enhance libdm deptree code to support data_offset (out-of-place reshaping)
and delta_disk (legs add/remove reshaping) target arguments
Related: rhbz834579
Related: rhbz1191935
Related: rhbz1191978
When cache volume may be converted from normal to -real layer LV
we need to improve logic for call cache_check.
With this patch, we register call for cache_check only when metadata LV
is not yet present in active table slot (should match initial table
load).
This avoids unwanted checking when cache would become layer device
online.
Activation of raid has brough up also splitted image with tracing
(without taking lock for this).
So when raid is now activate - such image is not put into
table (with _rmeta). When user needs such device, just active it.
Simplify info run for use only for INFO & STATUS.
Drop handling MKNODES within _info_run() call
and use more advanced _setup_task_run() directly.
This allows to further simplify _info_run().
Integrate also query for inactive table and
handle dm_task_run() and dm_task_get_info()
(thus switching to setup_task_run)
Add one exception case for DM_DEVICE_TARGET_MSG.
This allows further shortening and simplification of all
other users of this function.
Start moving selection of status taken for a LV into a single place.
The logic for showing info & status has been spread over multiple
places and were doing too complex decision going agains each other.
Unify selection of status of origin & cow scanned device.
TODO: in future we want to grab status for LV and layered LV and have
both statuses present for display - i.e. when 'old snapshot'
of thinLV is takes and there is ongoing merge - at some moment
we are not capable to show all needed info.
When lvm2 wants to see a status, it needs to validate,
segment for status reading is matching whan lvm2 expects in
metadata.
Also ensure status failure will not cause '0' from info reading
when actual info was collected properly.
Failure in 'status' reading is considered to be
a 'log_warn()' event only.
When we can't parse status, switch to warning as this is not
considered an errornous case. LVS is not supposed to return
error status code when device is not what it's been expected to
be - but it should be WARNING a user there is something unexpected.
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.
This patch fixes link validation for used thin-pool.
Udev rules correctly creates symlinks only for unused new thin-pool.
Such thin-pool can be used by foreing apps (like Docker) thus
has /dev/vg/lv link.
However when thin-pool becomes used by thinLV - this link is no
longer exposed to user - but internal verfication missed this
and caused messages like this to be printed upon 'vgchange -ay':
The link /dev/vg/pool should have been created by udev but it was not
found. Falling back to direct link creation.
And same with 'vgchange -an':
The link /dev/vg/pool should have been removed by udev but it is still
present. Falling back to direct link removal.
This patch ensures only unused thin-pool has this link.
Add more code to properly store status for snapshot segment
maintaining lvm2 fiction of COW and snapshot internal volumes.
The key issue here is however not though-through reporting
logic - as there is no single answer for whole line state.
It not counting with layer and we may need few more ioctl to
cover all reporting needs depending upon what is actually
needed.
In reality we need to 'cache' more ioctl status queries for
individual LVs and their segments (so they checked at most once).
The other 'hard' topic for conversion is mirror segment handling.
Also we definitelly need to relocate some logic into segment's methods,
yet it might be complex as we have not clear border between targets.
TODO: define more clearly how are reporting fields defined in case
we 'stack' volumes like - cache of stacked thin LV snapshot origin.
To get better control when flushing is used add extra arg when
setting up dm task.
By default now check dm device status without flush.
(At this moment this should effect only thin and cache volumes).
Also switch dev_manager_thin_pool_status() to use more
readable 'flush' parameter instead of 'no_flush'.
Improve code for snapshot merge for readabilty
and also reduce number of tests needed to decide
if merging can or cannot be started.
(Further improving 9cccf5245a)
To recognize in runtime if we are merging or not
to make consistent decision between suspend and resume
add function to parse thin table line when add
merging thin device to the table.
A snapshot merge into its origin cannot be initiated while the devices
are in use. If there is outside interference (such as from udev),
the suspend (preload) and resume stages can reach conflicting decisions
about whether or not to proceed.
Try to make the logic more robust by checking the inactive or live
table during resume. (This is still not perfect.)
When scanning if device is being usable as PV,
we call STATUS - but this status should not cause
any flushing.
Skip also open_count information as it's not needed.
Devices without "LVM-" uuid prefix have been generated by very old
version of lvm2 2.00 and 2.01.
Since version 2.02 all lvm2 devices are using prefix "LVM-".
However checking for present of ancient non prefixed devices does
take extra IOCTL per every call and for majority of todays user
it will not find anything new.
So use the assumption that users with kernel 3.X and newer are not
really using such old versions of lvm2 (year <2005) and with their
new kernel they are also using new version of lvm2 and skip
checking for them.
This change also makes trace logs more readable.
When leaving preload routine it should not altet state of flush required
when it's been already set to 1 and drop it to 0.
The API here is unclean, but current usage expects the same
variable pointer is for all preload calls and combines 'flush_required'
across all of them.
Commit 844b009584 tried to move
limit for usage of noflush to 'preload' however this was not
correctly processed.
Intead explicitly check for which types we do not want noflush
and also add debug message in this case.
Fix regression caused by commit ba41ee1dc9.
The idea was to use no_flush for changed device only for thin volumes
and thin pools but also to merge this with change made in commit
844b009584.
However the resulting condition has caused misbehavior for the mirror
suspend - as that has been before the ONLY allowed target type
that could have been suspended with noflush.
Result was badly working repair for --type mirror that has been
passing 'flush' to the repaired mirror target whenever preload
wrongly set flush_required.
The origin code has required the flush_required to be set whenever
deivce size is changed.
Now it first detects if device size got smaller
'dm_tree_node_size_changed(root) < 0' - this requires flush.
Otherwise it checks device is not thin volume nor thin pool and its
size has changed (got bigger) and requires flush.
This mean upsize of thin-pool or thin volume will not require flush.
Use meta% to expose highest mapped sector in thinLV.
so showing there 100.00% means thinLV maps latest sector.
Currently using a 'trick' with total_numerator to pass-in
device size when 'seg==NULL'
TODO: Improve device status API per target - current 'percentage'
is not really extensible.
Previous fix missed the fact the we do query for 'percent' with
seg value either set or unset (API overload...)
When 'seg' was unset, we still issue flush with status.
Fix it by cheking segtype by target_type.
As we check for segtype - we could also skip whole percentage
if the 'segtype' is unknown by code directly.
Reported-by: Ming-Hung Tsai <mingnus gmail com
Currently it's been checked for 'zero' header for thin-pool,
but lets use it always for cache as well - since it's relatively 'cheap'
detection of read 'error' problems as thin/cache tools
currently do not work fast enough in this case.
Fix reporting of Fail thin-pool target status
as attr[8] letter 'F'.
Report 'needs_check' status from thin-pool target via
attr field [4] (letter 'c'/'C'), and also via CheckNeeded field.
TODO: think about better name here?
TODO: lots of prop_not_implemented_set
Remove long outstand unused code lines, which were already
been obsoleted by other code.
Statuses and snapshot tree creation is already handled differently.
Also drop some 'extra' log_error() and use only stack;
since error has already been reported.
Since we do not use dev_manager in a way we would have destroyed VG
content while in-use - we could safely keep just pointer.
So dropping strdup.
Also it seems we actually no longer use vg_name for anything
so it may possibly go away completely unless it would be useful
for debugging...
When 'lvextend -L+XX vg/thinpool' do not leave inactive table
loaded for 'wrapping' LV on top of resized thin-pool
(ATM we use linear LV for this with same size as thin-pool).
Coverity noticed this condition is always false and the error
path could never be visited.
So check for all mismatches of supported messages
and actually mark log_error as internal error.
Recognize the target only 'extends' and do not enforce
'flush' in this case. Only the size reduction
still requires flush (so disables usage of no_flush flag).
If some other targets do require flush before suspend,
they have to explicitly ask for it.
While the activation code tries to evaluate which target
really needs flush with suspend and which may go without flush,
it has stayed effectively disabled by original commit:
33f732c5e9 since here
it only allows to pass non-pvmoving 'mirrors'.
So remove check for mirror LV type and only disable
no_flush for 'pvmove'..
TODO: Looking into history - it also seemed like raid target
would have always required flushing but it's been later
removed without clean explanation.
If some more targets really do need 'no_flush' it should
been handle at their 'level' - since we now stack multiple
targets over itself.
Since we may easily get blocked when checking for percentage
of thin-pool - do not flush and just show current values.
This avoids holding VG locked when pool is overfilled.
Try to detect thin-pool which my block lvm2 command from furher
processing (i.e. lvextend).
Check if pool is read-only or out-of-space and in this case thins
will skipped from being scanned (so user may miss some PVs located
on thin volumes).
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.)
Existing messaging intarface for thin-pool has a few 'weak' points:
* Message were posted with each 'resume' operation, thus not allowing
activation of thin-pool with the existing state.
* Acceleration skipped suspend step has not worked in cluster,
since clvmd resumes only nodes which are suspended (have proper lock
state).
* Resume may fail and code is not really designed to 'fail' in this
phase (generic rule here is resume DOES NOT fail unless something serious
is wrong and lvm2 tool usually doesn't handle recovery path in this case.)
* Full thin-pool suspend happened, when taken a thin-volume snapshot.
With this patch the new method relocates message passing into suspend
state.
This has a few drawbacks with current API, but overal it performs
better and gives are more posibilities to deal with errors.
Patch introduces a new logic for 'origin-only' suspend of thin-pool and
this also relates to thin-volume when taking snapshot.
When suspend_origin_only operation is invoked on a pool with
queued messages then only those messages are posted to thin-pool and
actual suspend of thin pool and data and metadata volume is skipped.
This makes taking a snapshot of thin-volume lighter operation and
avoids blocking of other unrelated active thin volumes.
Also fail now happens in 'suspend' state where the 'Fail' is more expected
and it is better handled through error paths.
Activation of thin-pool is now not sending any message and leaves upto a tool
to decided later how to finish unfinished double-commit transaction.
Problem which needs some API improvements relates to the lvm2 tree
construction. For the suspend tree we do not add target table line
into the tree, but only a device is inserted into a tree.
Current mechanism to attach messages for thin-pool requires the libdm
to know about thin-pool target, so lvm2 currently takes assumption, node
is really a thin-pool and fills in the table line for this node (which
should be ensured by the PRELOAD phase, but it's a misuse of internal API)
we would possibly need to be able to attach message to 'any' node.
Other thing to notice - current messaging interface in thin-pool
target requires to suspend thin volume origin first and then send
a create message, but this could not have any 'nice' solution on lvm2
side and IMHO we should introduce something like 'create_after_resume'
message.
Patch also changes the moment, where lvm2 transaction id is increased.
Now it happens only after successful finish of kernel transaction id
change. This change was needed to handle properly activation of pool,
which is in the middle of unfinished transaction, and also this corrects
usage of thin-pool by external apps like Docker.
Note that this is just a quick fix and it needs more robust fix to
encompass any combination, not just the (old) snapshot one!
This started with this report:
https://bugzilla.redhat.com/show_bug.cgi?id=1219222
If we have devices/ignore_suspended_devices=1 set based on which we
filter out suspended devices as unusable (or if we ignore suspended
devices by force, e.g. during lvconvert called from dmeventd) and
when we have snapshot and snapshot origin devices in the play, we
need to look at their components unerneath (*-real and *-cow) to
check if they're not suspended. If they are, the snapshot/snapshot
origin is not usable as well and hence it needs to be filtered out
by filter-usable.c code which does suspended device filtering.
Not going into much details here, more details are in the bugzilla
mentioned above. However, this is a quick fix since snapshot
and this exact situation is not the only one. So this is
something that needs to be revisited and fixed properly
with full dm tree and checking the whole stack to state
whether the device at the very top is usable or not.
Recently the single 'status' code has been used for number of cache
features.
Extend the API a little bit to allow usage also for lv_attr_dup.
As the function itself is used in lvm2api - add a new function:
lv_attr_dup_with_info_and_seg_status() that is able to use
grabbed info & status information.
report_init() is now using directly passed lvdm struct pointer
which holds the infomation whether lv_info() was correctly obtained or
there was some error when trying to read it.
Move 'healt' attribute to status.
TODO convert raid function to use the already known status.
At first, all snapshot-origins where marked as unusable unconditionally
here, but we can't cut off whole snapshot-origin use in a stack just
because of this possible mirror state. This whole "device_is_usable"
check was even incorrectly part of persistent filter before commit
a843d0d97c66aae1872c05b0f6cf4bda176aae2 (where filter cleanup was
done).
The persistent filter is used only if obtain_device_list_from_udev=0,
which means that the former check for snapshot-origin here had not even
been hit with default configuration for a few years before commit
a843d0d97c66aae1872c05b0f6cf4bda176aae2 (the check for snapshot-origin and
skipping of this LV was introduced with commit a71d6051ed
back in 2010).
The obtain_device_list_from_udev=1 (and hence not using persistent
filter and hence not hitting this check for snapshot-origins and skipping) has been
in action since commit edcda01a1e (that is 2011).
So for 3 years this condition was not even checked with default configuration,
making it superfluous.
This all changed in 2014 with commit 8a843d0d97
where "filter-usable" is introduced and since then all snapshot-origins
have been marked as unusable more often than before and making snapshot-origins
practically unusable in a stack.
This patch removes this incorrect check from commit a71d6051ed
which caused snapshot-origins to be unusable more often recently.
If we want to fix this eventually in a correct way, we need to look
down the stack and if snapshot-origin is hit and there's a blocked
mirror underneath, only then mark the device as unusable. But mirrors
in stack are not supported anymore so it's questionable whether it's
worth spending more time on this at all...
Fix regression introduced with a2c1024f6a
_setup_task(mknodes ? name : NULL...
has been replaced with:
_setup_task(type != MKNODES ? name : NULL....
Use '=='
We need to stop guessing deleted names - so rather collect
deleted UUID into a string list - and then remove them properly
in _clean_tree. Restore origin _clean_tree behaviour them for
currently unconverted removal of snapshots.
Pending delete feature now properly tracks whole subtree of cache
(so i.e. data or metadata as raid volumes).
It properly replaces all related volumes with 'errors' in suspend
preload, then resume them as error and remove collected UUIDs
from root - since they are not longer part of any volume deps.
LVM2.2.02.112/lib/metadata/cache_manip.c:73: overflow_before_widen: Potentially overflowing expression "*pool_metadata_extents *vg->extent_size" with type "unsigned int" (32 bits, unsigned) is evaluated using 32-bit arithmetic, and then used in a context that expects an expression of type "uint64_t" (64 bits, unsigned).
LVM2.2.02.112/lib/activate/dev_manager.c:217: overflow_before_widen: Potentially overflowing expression "seg_status->seg->len * extent_size" with type "unsigned int" (32 bits, unsigned) is evaluated using 32-bit arithmetic, and then used in a context that expects an expression of type "uint64_t" (64 bits, unsigned).
LVM2.2.02.112/lib/activate/dev_manager.c:217: overflow_before_widen: Potentially overflowing expression "seg_status->seg->le * extent_size" with type "unsigned int" (32 bits, unsigned) is evaluated using 32-bit arithmetic, and then used in a context that expects an expression of type "uint64_t" (64 bits, unsigned).
LVM2.2.02.112/lib/activate/dev_manager.c:196:5: warning: 'dmtask' may be used uninitialized in this function [-Wmaybe-uninitialized]
In _info_run fn:
switch (type) {
case INFO:
...
case STATUS:
...
case MKNODES:
...
}
The "type" is enum and currently only those three types are supported,
but if we added a new type in the future, this would end up with a bug
(if we forgot to add the new "case" in that "switch"). So let's make
sure proper internal error is printed:
default:
log_error(INTERNAL_ERROR "_info_run: unhandled info type");
return 0;
LVM2.2.02.112/tools/toollib.c:1991: leaked_storage: Variable "iter" going out of scope leaks the storage it points to.
LVM2.2.02.112/lib/filters/filter-usable.c:89: leaked_storage: Variable "f" going out of scope leaks the storage it points to.
LVM2.2.02.112/lib/activate/dev_manager.c:1874: leaked_handle: Handle variable "fd" going out of scope leaks the handle.
When getting status for LV segment types, we need to be sure
that proper segment is selected for the status ioctl.
When reporting fields that require status ioctl,
the "_choose_lv_segment_for_status_report" fn in tools/reporter.c
must be completed properly to choose the proper segment for all
the LV types (at the moment, it just takes the first LV segment
by default).
This works fine with cache LVs surely. The other segment types
need more auditing. We use this status ioctl only for cache status
fields at the moment only, so restrict it to the cache only.
Once the _choose_lv_segment_for_status_report is completed
properly, release the restriction in _get_segment_status_from_target_params.
Activate of new/unused/empty thin pool volume skips
the 'overlay' part and directly provides 'visible' thin-pool LV to the user.
Such thin pool still gets 'private' -tpool UUID suffix for easier
udev detection of protected lvm2 devices, and also gets udev flags to
avoid any scan.
Such pool device is 'public' LV with regular /dev/vgname/poolname link,
but it's still 'udev' hidden device for any other use.
To display proper active state we need to do few explicit tests
for this condition.
Before it's used for any lvm2 thin volume, deactivation is
now needed to avoid any 'race' with external usage.
Allowing 'external' use of thin-pools requires to validate even
so far 'unused' new thin pools.
Later we may have 'smarter' way to resolve which thin-pools are
owned by lvm2 and which are external.
