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When cache pool is reused for a new cached volume, there is
normally no need to 'keep' old cache-pool metadata as this
could cause major data lose.
Unlike with 'lvcreate -H -LX --cachepool' conversion, this lvconvert
path left the metadata unzeroed - partly for making easier some
debugging, but this was rather a bug.
So to keep possible reattach of 'unzeroed' metadata, user
now has to use 'lvconvert -Zn' for such conversion. In this case
the prompt will appear about possibe data loss and to proceed,
user has to confirm such operation. Without -Zn metadata are wiped.
Commit ca878a3426 changed behavior
or resize operation. Later the code has been futher changed
to skip fs resize completely when size of LV is already matching
and finaly at the most recent resize changeset for resize the
check for matching size has been eliminated as well so we ended
with a request call to resize fs to 0 size in some cases.
This commit reoders some test so the prompt happens just once before
resize of possibly 2 related volumes.
Also extra test for having LV already given size is added, and
whole metadata update is skipped for this case as the only
result would be an increment of seqno.
However the filesystem is still resized when requested,
so if the LV has some size and the resize is resolved to
the same size, the filesystem resize is called so in case FS
would not match, the resize will happen.
When logging to epoch files we would like to prevent creating too large
log files otherwise a spining command could fulfill available space
very easily and quickly.
Limit for to 100000 per command.
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.
This reverts commit fa69ed0bc8.
This code sometimes expects to be presented with a read-only filesystem
(during some boot sequences for example) and copes appropriately with
this and it should not lead to expected error messages that might cause
unnecessary alarm.
Add code to support more LVs to be resized through a same code path
using a single lvresize_params struct.
(Now it's used for thin-pool metadata resize,
next user will be snapshot virtual resize).
Update code to adjust percent amount resize for use_policies.
Properly activate inactive thin-pool in case of any pool resize
as the command should not 'deffer' this operation to next activation.
We have only 2 users of _lv_active() - one was already checking for ==1
while the other use (_lv_is_active()) could have take '-1' as a sign of having
an LV active. So return 0 and log_debug also the reason while detection
has failed (i.e. in case --driverload n - it's kind of expectable,
but might have confused user seeing just <backtrace>).
log_print is used during cmd line processing to log the result of the
operation (e.g. "Volume group vg successfully changed" and similar).
We don't want output from log_print to be interleaved with current
reports from group where log is reported as well. Also, the information
printed by log_print belongs to the log report too, so it should be
rerouted to log report if it's set.
Since the code in libdm-report which is responsible for doing the report
output uses log_print too, we need to use a different kind of log_print
which bypasses any log report currently used for logging (...simply,
we can't call log_print to output the log report itself which in turn
would again reroute to report - the report would never get on output
this way).
This patch adds structures and functions to reroute error and warning
logs to log report, if it's set.
There are 5 new functions:
- log_set_report
Set log report where logging will be rerouted.
- log_set_report_context
Set context globally so any report_cmdlog call will use it.
- log_set_report_object_type
Set object type globally so any report_cmdlog call will use it.
- log_set_report_object_name_and_id
Set object ID and name globally so any report_cmdlog call will use it.
- log_set_report_object_group_and_group_id
Set object group ID and name globally so any report_cmdlog call will use it.
These functions will be called during LVM command processing so any logs
which are rerouted to log report contain proper information about current
processing state.
The lvm fullreport works per VG and as such, the vg, lv, pv, seg and
pvseg subreport is done for each VG. However, if the PV is not part of
any VG yet, we still want to display pv and pvseg subreports for these
"orphan" PVs - so enable this for lvm fullreport's process_each_vg call.
Groupable args (the ones marked with ARG_GROUPABLE flag) start a new
group of args if:
- this is the first time we hit such a groupable arg,
- or if non-countable arg is repeated.
However, there may be cases where we want to give priorities when
forming groups and hence force new group creation if we hit an arg
with higher grouping priority.
For example, let's assume (for now) hypothetical sequence of args used:
lvs -o lv_name --configreport log -o log_type --configreport lv -o +vg_name
Without giving any priorites, we end up with:
lvs -o lv_name --configreport log -o log_type --configreport lv -o +vg_name
| | | | | |
\__________GROUP1___________/ \________GROUP2___________/ \_GROUP3_/
This is because we hit "-o" as the first groupable arg. The --configreport,
even though it's groupable too, it falls into the previous "-o" group.
While we may need to give priority to the --configreport arg that should
always start a new group in this scenario instead:
lvs -o lv_name --configreport log -o log_type --configreport lv -o +vg_name
| | | | | |
\_GROUP1_/ \_________GROUP2___________/ \_________GROUP3__________/
So here "-o" started a new group but since "--configreport" has higher
priority than "-o", it starts fresh new group now and hence the rest of
the command line's args are grouped by --configreport now.
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.
Wire up report group creation with log report in struct
processing_handle and call report_format_init during processing handle
initialization (init_processing_handle fn) and destroy it while
destroing processing handle (destroy_processing_handle fn).
This way, all the LVM command processing using processing handle
has access to log report via which the current command log
can be reported as items are processed.
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)
Add new --reportformat option and new report_format_init function that
checks this option and creates new report group accordingly, also
preparing log report handle and adding it to the report group just
created.
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.
Original code missed to catch all apperances of SIGINT.
Also enhance logging when running in shell without tty.
Accept this regex as valid input:
'^[ ^t]*([Yy]([Ee]([Ss]|)|)|[Nn]([Oo]|))[ ^t]*$'
Commit #5b3a4a9 caused the "name" variable to be cleared if
declaration and assignment is on two lines so put it back
so it's on one line for it to work again.
If configuration consists of several sources in config cascade
("config cascade" defined in man lvmconfig(8)), lvmconfig displayed
only difference from defaults of the topmost config in the cascade.
Fix lvmconfig to display complete difference, considering all
the configuration in the cascade.
For example, before this patch:
(use_lvmetad=0 set in lvm.conf which differs from defaults)
$ lvmconfig --type diff
global {
use_lvmetad=0
}
(compact_output=1 set on cmd line)
$ lvmconfig --type diff --config report/compact_output=1
report {
compact_output=1
}
(headings=0 set in profile)
$ lvmconfig --type diff --commandprofile test
report {
headings=0
}
(difference in topmost configuration source is displayed)
$ lvmconfig --type diff --commandprofile test --config report/compact_output=1
report {
compact_output=1
}
With this patch applied (the config cascade is merged before looking for
difference from defaults in configuration):
$ lvmconfig --type diff
global {
use_lvmetad=0
}
$ lvmconfig --type diff --config report/compact_output=1
report {
compact_output=1
}
global {
use_lvmetad=0
}
$ lvmconfig --type diff --profile test
report {
headings=0
}
global {
use_lvmetad=0
}
$ lvmconfig --type diff --profile test --config report/compact_output=1
report {
headings=0
compact_output=1
}
global {
use_lvmetad=0
}
Treat loop device created with 'losetup -P' as regular
partitioned device - so if it has partition table,
prevent its usage in commands like 'pvcreate'.
Before 'pvcreate /dev/loop0' could have erased and formated as PV,
after this patch, device is filtered out and cannot be used.
Before this fix, when reporting 'lvm devtypes', the report was
initialized with incorrect reserved values - the ones used for
pvs/vgs/lvs report were used instead of NULL value (because devtypes
doesn't have any reserved values).
For example, trying to (incorrectly) use lv_name for the -S|--select
with lvm devtypes which doesn't have this field at all:
Before this patch (internal error issued):
$ lvm devtypes -S 'lv_name=lvol0'
Internal error: _check_reserved_values_supported: field-specific reserved value of type 0x0 for field not supported
Internal error: dm_report_init_with_selection: trying to register unsupported reserved value type, skipping report selection
DevType MaxParts Description
aoe 16 ATA over Ethernet
ataraid 16 ATA Raid
bcache 1 bcache block device cache
...
With this patch applied (correct error displayed about
unrecognized selection field):
$ lvm devtypes -S 'lv_name=lvol0'
Device Types Fields
-------------------
devtype_name - Name of Device Type exactly as it appears in /proc/devices. [string]
devtype_max_partitions - Maximum number of partitions. (How many device minor numbers get reserved for each device.) [number]
devtype_description - Description of Device Type. [string]
Special Fields
--------------
selected - Set if item passes selection criteria. [number]
help - Show help. [unselectable number]
? - Show help. [unselectable number]
Unrecognised selection field: lv_name
Selection syntax error at 'lv_name=lvol0'.
Use 'help' for selection to get more help.
Convert fields into using a single status ioctl call per LV.
This is a bit tricky since when there are more complicated
stacks, at this moment its undefined which values should be shown.
It's clear we need to cache more then single ioctl per LV,
but also we need to define more explicitely relation between
reported values for snapshots.
This patch is not a final state, rather a transitional step.
It should not be giving more 'worst' values then previous
many-ioctl-calls-per-lv solution.
Add function to obtain percentage value for cache lv_seg_status.
This API is rather evolving 'middle' step as the ultimate goal
is segment API fuctionality.
But first we need to be clear at reporting level which values
are needed to be reported for which LVs and segments.
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.
lv_refresh_suspend_resume() has escaped with fail ret code
after failing suspend and could have left many volumes in suspend state.
So always unconditionally call resume also when suspend has failed.
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'.
Check first the LV is cow before even checking it's a merging COW.
Note: previosly merging_cow was also merging origin, so without
this explicit check it used to return '1' also when passed
LV has been merging origin.
When mirror/raid called copy_percent function to return,
when 100% was supposed to be returned, wrong float 100.0 value
could have been reported back instead of dm_percent_t DM_PERCENT_100.
There is broken API somewhere, since the function here rely on
actively being modifid VG content even when doing 'lvs' operation.
(extents_copies)
Add support for active cache LV.
Handle --cachemode args validation during command line processing.
Rework some lvm2 internal to use lvm2 defined CACHE_MODE enums
indepently on libdm defines and use enum around the code instead
of passing and comparing strings.
Support parsing --chunksize option also when converting.
Now user can use cache pool created with i.e. 32K chunksize,
while in caching user can select 512K blocks.
Tool is supposed to validate cache metadata size is big enough
to support such chunk size. Otherwise error is shown.
If there's an activation volume_filter, it might not be possible
to activate the rmeta LVs to wipe them. At least inherit any
LV tags from the parent LV while attempting this.
Before executing modprobe for given module name, just check
if the module is not already present in /sys/module.
Useful when checking dm-cache-policy modules as we do not
having matching interface like for targets.
vg/snapshotN should not appear anywhere.
No code should be showing this, but it was noticed in some logs last
week and we can deal with it in display_lvname().
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.)
Commit 971ab733b7 ("thin: activation of
merging thin snapshot") also added an incorrect deactivation attempt
for non-thin LVs: find_snapshot(lv)->lv is not designed to be
activated and any attempt to deactivate it is incorrect.
When not obtaining device from udev, we are doing deep devdir scan,
and at the same time we try to insert everything what /sys/dev/block
knows about. However in case lvm2 is configured to use nonstardard
devdir this way it will see (and scan) devices from a real system.
lvm2 test suite is using its own test devdir with its
own device nodes. To avoid touching real /dev devices, validate
the device node exist in give dir and do not insert such device
into a cache.
With obtain list from udev this patch has no effect
(the normal user path).
We have _insert_dirs() for udev and non-udev compilation.
Compiling without udev missed to call dev_cache_index_devs().
Move the call after _insert_dirs() call so both compilation
gets it.
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.
This is hotfix for RHBZ: https://bugzilla.redhat.com/1324537
However already the %FREE is not a good fit and we need something
better. Meanwhile make -l%PVS work at least as good as %FREE
for thin-pool.
TODO: this needs rework - it should be allocator to do all the size
decisions at one place.
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
It's correct to have a DM device that has no DM UUID assigned
so no need to issue error message in this case. Also, if the
device doesn't have DM UUID, it's also clear it's not an LVM LV
(...when looking for VGID/LVID while creating VGID/LVID indices
in dev cache).
For example:
$ dmsetup create test --table "0 1 linear /dev/sda 0"
And there's no PV in the system.
Before this patch (spurious error message issued):
$ pvs
_get_sysfs_value: /sys/dev/block/253:2/dm/uuid: no value
With this patch applied (no spurious error message):
$ pvs
If we're using persistent .cache file, we're reading this file instead
of traversing the /dev content. Fix missing indexing by VGID and LVID
here - hook this into persistent_filter_load where we populate device
cache from persistent .cache file instead of scanning /dev.
For example, inducing situation in which we warn about different device
actually used than what LVM thinks should be used based on metadata:
$ lsblk -s /dev/vg/lvol0
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vg-lvol0 253:4 0 124M 0 lvm
`-loop1 7:1 0 128M 0 loop
$ lvmconfig --type diff
global {
use_lvmetad=0
}
devices {
obtain_device_list_from_udev=0
}
(obtain_device_list_from_udev=0 also means the persistent .cache file is used)
Before this patch - pvs is fine as it does the dev scan, but lvs relies
on persistent .cache file and it misses the VGID/LVID indices to check
and warn about incorrect devices used:
$ pvs
Found duplicate PV B9gXTHkIdEIiMVwcOoT2LX3Ywh4YIHgR: using /dev/loop0 not /dev/loop1
Using duplicate PV /dev/loop0 without holders, ignoring /dev/loop1
WARNING: Device mismatch detected for vg/lvol0 which is accessing /dev/loop1 instead of /dev/loop0.
PV VG Fmt Attr PSize PFree
/dev/loop0 vg lvm2 a-- 124.00m 0
$ lvs
Found duplicate PV B9gXTHkIdEIiMVwcOoT2LX3Ywh4YIHgR: using /dev/loop0 not /dev/loop1
Using duplicate PV /dev/loop0 without holders, ignoring /dev/loop1
LV VG Attr LSize
lvol0 vg -wi-a----- 124.00m
With this patch applied - both pvs and lvs is fine - the indices are
always created correctly (lvs just an example here, other LVM commands
that rely on persistent .cache file are fixed with this patch too):
$ pvs
Found duplicate PV B9gXTHkIdEIiMVwcOoT2LX3Ywh4YIHgR: using /dev/loop0 not /dev/loop1
Using duplicate PV /dev/loop0 without holders, ignoring /dev/loop1
WARNING: Device mismatch detected for vg/lvol0 which is accessing /dev/loop1 instead of /dev/loop0.
PV VG Fmt Attr PSize PFree
/dev/loop0 vg lvm2 a-- 124.00m 0
$ lvs
Found duplicate PV B9gXTHkIdEIiMVwcOoT2LX3Ywh4YIHgR: using /dev/loop0 not /dev/loop1
Using duplicate PV /dev/loop0 without holders, ignoring /dev/loop1
WARNING: Device mismatch detected for vg/lvol0 which is accessing /dev/loop1 instead of /dev/loop0.
LV VG Attr LSize
lvol0 vg -wi-a----- 124.00m
It's possible that while a device is already referenced in sysfs, the node
is not yet in /dev directory.
This may happen in some rare cases right after LVs get created - we sync
with udev (or alternatively we create /dev content ourselves) while VG
lock is held. However, dev scan is done without VG lock so devices may
already be in sysfs, but /dev may not be updated yet if we call LVM command
right after LV creation (so the fact that fs_unlock is done within VG
lock is not usable here much). This is not a problem with devtmpfs as
there's at least kernel name for device in /dev as soon as the sysfs
item exists, but we still support environments without devtmpfs or
where different directory for dev nodes is used (e.g. our test suite).
This patch covers these situations by tracking such devices in
_cache.sysfs_only_names helper hash for the vgid/lvid check to work still.
This also resolves commit 6129d2e64d
which was then reverted by commit 109b7e2095
due to performance issues it may have brought (...and it didn't resolve
the problem fully anyway).
It's possible for an LVM LV to use a device during activation which
then differs from device which LVM assumes based on metadata later on.
For example, such device mismatch can occur if LVM doesn't have
complete view of devices during activation or if filters are
misbehaving or they're incorrectly set during activation.
This patch adds code that can detect this mismatch by creating
VG UUID and LV UUID index while scanning devices for device cache.
The VG UUID index maps VG UUID to a device list. Each device in the
list has a device layered above as a holder which is an LVM LV device
and for which we know the VG UUID (and similarly for LV UUID index).
We can acquire VG and LV UUID by reading /sys/block/<dm_dev_name>/dm/uuid.
So these indices represent the actual state of PV device use in
the system by LVs and then we compare that to what LVM assumes
based on metadata.
For example:
[0] fedora/~ # lsblk /dev/sdq /dev/sdr /dev/sds /dev/sdt
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sdq 65:0 0 104M 0 disk
|-vg-lvol0 253:2 0 200M 0 lvm
`-mpath_dev1 253:3 0 104M 0 mpath
sdr 65:16 0 104M 0 disk
`-mpath_dev1 253:3 0 104M 0 mpath
sds 65:32 0 104M 0 disk
|-vg-lvol0 253:2 0 200M 0 lvm
`-mpath_dev2 253:4 0 104M 0 mpath
sdt 65:48 0 104M 0 disk
`-mpath_dev2 253:4 0 104M 0 mpath
In this case the vg-lvol0 is mapped onto sdq and sds becauset this is
what was available and seen during activation. Then later on, sdr and
sdt appeared and mpath devices were created out of sdq+sdr (mpath_dev1)
and sds+sdt (mpath_dev2). Now, LVM assumes (correctly) that mpath_dev1
and mpath_dev2 are the PVs that should be used, not the mpath
components (sdq/sdr, sds/sdt).
[0] fedora/~ # pvs
Found duplicate PV xSUix1GJ2SK82ACFuKzFLAQi8xMfFxnO: using /dev/mapper/mpath_dev1 not /dev/sdq
Using duplicate PV /dev/mapper/mpath_dev1 from subsystem DM, replacing /dev/sdq
Found duplicate PV MvHyMVabtSqr33AbkUrobq1LjP8oiTRm: using /dev/mapper/mpath_dev2 not /dev/sds
Using duplicate PV /dev/mapper/mpath_dev2 from subsystem DM, ignoring /dev/sds
WARNING: Device mismatch detected for vg/lvol0 which is accessing /dev/sdq, /dev/sds instead of /dev/mapper/mpath_dev1, /dev/mapper/mpath_dev2.
PV VG Fmt Attr PSize PFree
/dev/mapper/mpath_dev1 vg lvm2 a-- 100.00m 0
/dev/mapper/mpath_dev2 vg lvm2 a-- 100.00m 0
The /proc/self/mountinfo is not bound to device names like /proc/mounts
and it uses major:minor pairs instead.
This fixes a situation in which a volume is mounted and then renamed
later on - that makes /proc/mounts unreliable when detecting mounted
volumes.
See also https://bugzilla.redhat.com/show_bug.cgi?id=1196910.
Commit b64703401d cause regression
when handling stacked resize of pool metadata volume that would
be a raid LV.
Fix it by properly setting up size also for layer extension.
Continuing with lvconvert style updates.
Minimize usage of '\:' as zero-width break space, since html renderers
do not handle this groff sign well (some of them seems to even render
':' there).
But since we do not want see badly rendered man pages itself, prefer
the 'man visual' appearence over html page generation (man2html should
be actually fixed).
Start to use 'user input option' with Capitals more consistently.
Fixing vpath usage as it has been checking for existance of
generated file also in the $(scrdir) e.g.:
No need to remake target '10-dm.rules.in'; using VPATH name '...'
If the $(srcdir) had been also $(builddir) and contained already
generated rules file, it's been used instead generating new
one.
(See: http://make.mad-scientist.net/papers/how-not-to-use-vpath/)
Commit abd9618dd8 tried to improve
parsing of vg name from logical path - but still missed couple
corner cases.
This patch further improves the logic and reuses
validate_lvname_param() for parsing of lv_name.
Also explicitly checks for LVM_VG_NAME in the right case.
So now also properly parses cases like:
'lvconvert --repairt vg/'
and will provide correct error message.
Specifying an output width of 0 now leads to a default minimum width
taken from the width of the column heading. (Most fields should use
this.)
Components of field names are generally separated by underscores (which
are optional at run-time). (Dropped 3 duplicate fields now covered by
this rule.)
Each field heading must be unique and generally doesn't have spaces
between words (which get capitalised) unless they are already short and
the fields are normally longer or clarity demands it.
This command option can be used to trigger a D-Bus
notification independent of the usual notifications
that are sent from other commands as an effect of
changes to PV/VG/LV state. If lvm is not built with
dbus notification support or if notify_dbus is disabled
in the config, this command will exit with an error.
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.
Pair kernel_cache_settings with kernel_cache_policy.
There is very small chance in error case that the value in table
might be differnet from the value stored in metadata
so make it 'checkable'.
