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Some commands scan labels to populate lvmcache multiple
times, i.e. lvmcache_init, scan labels to fill lvmcache,
lvmcache_destroy, then later repeat
Each time labels are scanned, duplicates are detected,
and preferred devices are chosen. Each time this is done
within a single command, we want to choose the same
preferred devices. So, check for existing preferences
when choosing preferred devices.
This also fixes a problem with the list of unused duplicate
devs when run in an lvm shell. The devs had been allocated
from cmd memory, resulting in invalid list entries between
commands.
A program may be using liblvm2app for simply checking a config
setting in lvm.conf. In this case, a full lvm context is not
needed, only cmd->cft (which are the config settings read from
lvm.conf).
lvm_config_find_bool() can now be passed a NULL lvm context
in which case it will only create cmd->cft, check the config
setting asked for, and destroy the cmd.
When setting up a toolcontext, the lib init function
was detecting an error when there was none, and then
it was returning an incompletely initialized cmd struct
instead of NULL. The effect was that the lib would try
to use the uninitialized cmd struct and segfault.
This would happen if a non-fatal error occurred during
cmd setup, e.g. user permission failed on lvmetad socket,
causing cmd to fall back to scanning and not use lvmetad.
The only real error condition is when create_toolcontext
returns NULL. If cmd is returned, the lib can use it.
If lvmetad is running, and a command opts to not use it
(--config global/use_lvmetad=0), and the command changes
metadata, then the metadata change is not visible to
lvmetad. Subsequent commands using lvmetad to change
metadata may cause corruption based on the invalid
lvmetad state.
Eventually we can set the disabled state in lvmetad
to prevent this problem, but for now print a warning
about the possibility.
When command is not using lvmetad because
use_lvmetad=0 in the config, but the lvmetad
pidfile exists, print a warning (previously
this checked for the socket existing instead
of the pidfile existing.)
The lvmetad connection is created within the
init_connections() path during command startup,
rather than via the old lvmetad_active() check.
The old lvmetad_active() checks are replaced
with lvmetad_used() which is a simple check that
tests if the command is using/connected to lvmetad.
The old lvmetad_set_active(cmd, 0) calls, which
stopped the command from using lvmetad (to revert to
disk scanning), are replaced with lvmetad_make_unused(cmd).
When a command modifies a PV or VG, or changes the
activation state of an LV, it will send a dbus
notification when the command is finished. This
can be enabled/disabled with a config setting.
This patch adds "include_historical_lvs" field to struct cmd_context to
make it possible for the command to switch between original funcionality
where no historical LVs are processed and functionality where historical
LVs are taken into account (and reported or processed further). The switch
between these modes is done using the '-H|--history' switch on command
line.
The include_historical_lvs state is then passed to process_each_* fns
using the "include_historical_lvs" field within struct processing_handle.
'verbose' was marked as a boolean option while it
takes integer args - so it has limited usage to 0 or 1,
but we supported 0-4 at least.
Fix it by switching to corrent int type.
(Hopefully noone was trying to use this variable as true/yes/false/no
way - as the would be unsupported/undocumented).
The regex filter (controlled by devices/filter lvm.conf setting) was
evaluated as the very last filter. However, this is not optimal when
it comes to restricting disk access - users define devices/filter
as well as devices/global_filter to avoid this.
The devices/global_filter is already positioned at the beginning of the
filter chain. We need to do the same for devices/filter.
Filter chains before this patch:
A: when lvmetad is not used:
persistent_filter -> sysfs_filter -> global_regex_filter ->
type_filter -> usable->filter -> mpath_component_filter ->
partition_filter -> md_component_filter -> fw_raid_filter ->
regex_filter
B: when lvmetad is used:
B1: to update lvmetad:
sysfs_filter -> global_regex_filter -> type_filter ->
usable_filter -> mpath_component_filter -> partition_filter ->
md_component_filter -> fw_raid_filter
B2: to retrieve info from lvmetad:
persistent_filter -> usable_filter -> regex_filter
From the chain list above we can see that particularly in case when
lvmetad is not used, the regex filter is the very last one that is
processed. If lvmetad is used, it doesn't matter much as there's
the global_regex_filter which is used instead when updating lvmetad
and when retrieving info from lvmetad, putting regex_filter in front
of usable_filter wouldn't change much since usabled_filter is not
reading disks directly.
This patch puts the regex filter to the front even in case lvmetad
is not used, hence reinstating the state as it was before commit
a7be3b12df (which moved the regex_filter
position in the chain). Still, the arguments for the commit
a7be3b12df still apply and they're
still satisfied since component filters (MD, mpath...) are evaluated
first just before updating lvmetad.
So with this patch, we end up with:
A: when lvmetad is not used:
persistent_filter -> sysfs_filter -> global_regex_filter ->
regex_filter -> type_filter -> usable->filter ->
mpath_component_filter -> partition_filter ->
md_component_filter -> fw_raid_filter
B: when lvmetad is used:
B1: to update lvmetad:
sysfs_filter -> global_regex_filter -> type_filter ->
usable_filter -> mpath_component_filter -> partition_filter ->
md_component_filter -> fw_raid_filter
B2: to retrieve info from lvmetad:
persistent_filter -> regex_filter -> usable_filter
This way, specifying the regex_filter in non-lvmetad case causes
the devices to be filtered based on regex first before processing
any other filters which can access disks (like md_component_filter).
This patch also streamlines the code for better readability.
Previously, a command would only rescan a lockd VG
when lvmetad returned the "vg_invalid" flag indicating
that the cached copy was invalid (which is done by
lvmlockd.) This is still the only usual reason for
rescanning a lockd VG, but two new special cases are
added where we also do the rescan:
. When the --shared option is used to display lockd VGs
from hosts not using lvmlockd. This is the same case
as using --foreign to display foreign VGs, but --shared
was missing the corresponding bits to rescan the VGs.
. When a lockd VG is allowed to be read for displaying
after failing to acquire the lock from lvmlockd. In
this case, the usual mechanism for validating the
cache is missed, so assume the cache would have been
invalidated. (This had been a previous todo item
that was lost during other cleanup.)
These were long-standing todos that were lost track of.
When vgremove is used to remove multiple VGs in one command,
e.g. vgremove foo bar, the first VG (foo) that is removed
may have held the sanlock global lock. In this case,
do not continue removing further VGs (bar) without the
global lock.
Use refresh_filters instead of destroy_filters and init_filters
in refresh_toolcontext fn which deals with cmd->initialized.filters
correctly on refresh.
Just shuffle the items and put them into logical groups so it's
visible at first sight what each group contains - it makes it a bit
easier to make heads and tails of the whole cmd_context monster.
Make it possible to decide whether we want to initialize connections and
filters together with toolcontext creation.
Add "filters" and "connections" fields to struct
cmd_context_initialized_parts and set these in cmd_context.initialized
instance accordingly.
(For now, all create_toolcontext calls do initialize connections and
filters, we'll change that in subsequent patch appropriately.)
Move original lvmetad and lvmpolld initialization code from
_process_config fn to their own functions _init_lvmetad and
_init_lvmpolld (both covered with single _init_connections fn).
Add struct cmd_context_initialized_parts to wrap up information
about which cmd context pieces are initialized and add variable
of this struct type into struct cmd_context.
Also, move existing "config_initialized" variable that was directly
part of cmd_context into the new cmd_context.initialized wrapper.
We'll be adding more items into the struct cmd_context_initialized_parts
with subsequent patches...
The vgchange/lvchange activation commands read the VG, and
don't write it, so they acquire a shared VG lock from lvmlockd.
When other commands fail to acquire a shared VG lock from
lvmlockd, a warning is printed and they continue without it.
(Without it, the VG metadata they display from lvmetad may
not be up to date.)
vgchange/lvchange -a shouldn't continue without the shared
lock for a couple reasons:
. Usually they will just continue on and fail to acquire the
LV locks for activation, so continuing is pointless.
. More importantly, without the sh VG lock, the VG metadata
used by the command may be stale, and the LV locks shown
in the VG metadata may no longer be current. In the
case of sanlock, this would result in odd, unpredictable
errors when lvmlockd doesn't find the expected lock on
disk. In the case of dlm, the invalid LV lock could be
granted for the non-existing LV.
The solution is to not continue after the shared lock fails,
in the same way that a command fails if an exclusive lock fails.
Use find_config_tree_array for all config arrays. Also, add
INTERNAL_ERROR in case there should have been at least default
value defined for a setting but it was not returned for some
reason (either config_settings.h misconfiguration or other config
tree error printed by functions called by find_config_tree_array).
Before, we used general find_config_tree_node function to retrieve
array values. This had a downside where if the node was not found,
we had to insert default values directly in-situ after the
find_config_tree_node call. This way, we had two copies of default
values - one in config_settings.h and the other one directly in the
code where we found out that find_config_tree_node returned NULL and
hence we needed to fall back to defaults.
With separate find_config_tree_array used for array config values,
we keep all the defaults centrally in config_settings.h because
the new find_config_tree_array automatically returns these defaults
if it can't find any value set in the configuration.
This patch just makes the behaviour exactly the same for arrays as
for any other non-array type where we call find_config_tree_<type>
already, hence making the internal interface for handling array
values consistent with the rest of the config types.
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.
Make it possible to define format for time that is displayed.
The way the format is defined is equal to the way that is used
for strftime function, although not all formatting options as
used in strftime are available for LVM2 - the set is restricted
(e.g. we do not allow newline to be printed). The lvm.conf
comments contain the whole list that LVM2 accepts for time format
together with brief description (copied from strftime man page).
For example:
(defaults used - the format is the same as used before this patch)
$ lvs -o+time vg/lvol0 vg/lvol1
LV VG Attr LSize Time
lvol0 vg -wi-a----- 4.00m 2015-06-25 16:18:34 +0200
lvol1 vg -wi-a----- 4.00m 2015-06-29 09:17:11 +0200
(using 'time_format = "@%s"' in lvm.conf - number of seconds
since the Epoch)
$ lvs -o+time vg/lvol0 vg/lvol1
LV VG Attr LSize Time
lvol0 vg -wi-a----- 4.00m @1435241914
lvol1 vg -wi-a----- 4.00m @1435562231
Use of display_lvname() in plain log_debug() may accumulate memory in
command context mempool. Use instead small ringbuffer which allows to
store cuple (10 ATM) names so upto 10 full names can be used at one.
We are not keeping full VG/LV names as it may eventually consume larger
amount of RAM resouces if vgname is longer and lots of LVs are in use.
Note: if there would be ever needed for displaing more names at once,
the limit should be raised (e.g. log_debug() would need to print more
then 10 LVs on a single line).
In log messages refer to it as system ID (not System ID).
Do not put quotes around the system_id string when printing.
On the command line use systemid.
In code, metadata, and config files use system_id.
In lvmsystemid refer to the concept/entity as system_id.
The only realistic way for a host to have active LVs in a
foreign VG is if the host's system_id (or system_id_source)
is changed while LVs are active.
In this case, the active LVs produce an warning, and access
to the VG is implicitly allowed (without requiring --foreign.)
This allows the active LVs to be deactivated.
In this case, rescanning PVs for the VG offers no benefit.
It is not possible that rescanning would reveal an LV that
is active but wasn't previously in the VG metadata.
A foreign VG should be silently ignored by a reporting/display
command like 'vgs'. If the reporting/display command specifies
a foreign VG by name on the command line, it should produce an
error message.
Scanning commands pvscan/vgscan/lvscan are always allowed to
read and update caches from all PVs, including those that belong
to foreign VGs.
Other non-report/display/scan commands always ignore a foreign
VG, or report an error if they attempt to use a foreign VG.
vgimport should always invalidate the lvmetad cache because
lvmetad likely holds a pre-vgexported copy of the VG.
(This is unrelated to using foreign VGs; the pre-vgexported
VG may have had no system_id at all.)
Move the lvm1 sys ID into vg->lvm1_system_id and reenable the #if 0
LVM1 code. Still display the new-style system ID in the same
reporting field, though, as only one can be set.
Add a format feature flag FMT_SYSTEM_ON_PVS for LVM1 and disallow
access to LVM1 VGs if a new-style system ID has been set.
Treat the new vg->system_id as const.
Allow cmd->unknown_system_id to be cleared during toolcontext
refresh.
Set a default value of "none" for global/system_id_source.
Allow local/system_id to be empty so it's not impossible for
a later config file to remove it.
In a file containing a system ID:
Any whitespace at the start of a line is ignored;
Blank lines are ignored;
Any characters after a # are ignored along with the #.
The system ID is obtained by processing the first line with
non-ignored characters.
If further lines with non-ignored characters follow, a warning is
issued.
Add WARNING messages if there are problems setting the requested
system ID.
Ban "localhost" as a prefix regardless of the system_id_source.
Use cmd->hostname instead of calling uname again.
Make system_id_source values case-insensitive (as with new settings like
log_debug_classes) and also accept machine-id to match the filename.
Require system ID to begin with an alphanumeric character.
Rename fn to make clear it's only validation for systemid
and always terminate result rather than imposing this on the caller.
In 2.02.99, _init_tags() inadvertently began to ignore the
dm_config_tree struct passed to it. "tags" sections are not
merged together, so the "tags" section in the main config file was
being processed repeatedly and other "tags" sections were ignored.
Just like MD filtering that detects components of software RAID (md),
add detection for firmware RAID.
We're not adding any native code to detect this - there are lots of
firmware RAIDs out there which is just out of LVM scope. However,
with current changes with which we're able to get device info from
external sources (e.g. external_device_info_source="udev"), we can
do this easily if the external device status source has this kind
of information - which is the case of "udev" source where the results
of blkid scans are stored.
This detection should cover all firmware RAIDs that blkid can detect and
which are identified as:
ID_FS_TYPE = {adaptec,ddf,hpt45x,hpt37x,isw,jmicron,lsi_mega,nvidia,promise_fasttrack,silicon_medley,via}_raid_member
Composite filter is a filter that can put several filters in one set.
This patch adds a switch when creating the composite filter which will
enable or disable external device info handles for all the filters
the composite filter encompasses.
We want to use this external device info for majority of the filters
which are in the "lvmetad filter chain" (or the respective part if
we're not using lvmetad).
Following patches will use the enabled external device handle in
concrete filters from the composite filter...
There are actually three filter chains if lvmetad is used:
- cmd->lvmetad_filter used when when scanning devices for lvmetad
- cmd->filter used when processing lvmetad responses
- cmd->full_fiilter (which is just cmd->lvmetad_filter + cmd->filter chained together) used
for remaining situations
This patch adds the third one - "cmd->full_filter" - currently this is
used if device processing does not fall into any of the groups before,
for example, devices which does not have the PV label yet and we're just
creating a new one or we're processing the devices where the list of the
devices (PVs) is not returned by lvmetad initially.
Currently, the cmd->full_filter is used exactly in these functions:
- lvmcache_label_scan
- _pvcreate_check
- pvcreate_vol
- lvmdiskscan
- pvscan
- _process_each_label
If lvmetad is used, then simply cmd->full_filter == cmd->filter because
cmd->lvmetad_filter is NULL in this case.
We need to use proper filter chain when we disable lvmetad use
explicitly in the code by calling lvmetad_set_active(0) while
overriding existing configuration. We need to reinitialize filters
in this case so proper filter chain is used. The same applies
for the other way round - when we enable lvmetad use explicitly in
the code (though this is not yet used).
With this change, the filter chains used look like this now:
A) When *lvmetad is not used*:
- persistent filter -> regex filter -> sysfs filter ->
global regex filter -> type filter ->
usable device filter(FILTER_MODE_NO_LVMETAD) ->
mpath component filter -> partitioned filter ->
md component filter
B) When *lvmetad is used* (two separate filter chains):
- the lvmetad filter chain used when scanning devs for lvmetad update:
sysfs filter -> global regex filter -> type filter ->
usable device filter(FILTER_MODE_PRE_LVMETAD) ->
mpath component filter -> partitioned filter ->
md component filter
- the filter chain used for lvmetad responses:
persistent filter -> usable device filter(FILTER_MODE_POST_LVMETAD) ->
regex filter
Caused by recent changes - a7be3b12df.
If global filter was not defined, then part of the code
creating composite filter (the cmd->lvmetad_filter) incorrectly
increased index value even if this global filter was not created
as part of the composite filter. This caused a gap with "NULL"
value in the composite filter array which ended up with the rest
of the filters after the gap to be ignored and also it caused a mem
leak when destroying the composite filter.
If a PV label is exposed both through a composite device (MD for example) and
through its component devices, we always want the PV that lvmetad sees to be the
composite, since this is what all LVM commands (including activation) will then
use. If pvscan --cache is triggered for multiple clones of the same PV, the last
to finish wins. This patch basically re-arranges the filters so that
component-device filters are part of the global_filter chain, not of the
client-side filter chain. This has a subtle effect on filter evaluation order,
but should not alter visible semantics in the non-lvmetad case.
Currently, we have two modes of activation, an unnamed nominal mode
(which I will refer to as "complete") and "partial" mode. The
"complete" mode requires that a volume group be 'complete' - that
is, no missing PVs. If there are any missing PVs, no affected LVs
are allowed to activate - even RAID LVs which might be able to
tolerate a failure. The "partial" mode allows anything to be
activated (or at least attempted). If a non-redundant LV is
missing a portion of its addressable space due to a device failure,
it will be replaced with an error target. RAID LVs will either
activate or fail to activate depending on how badly their
redundancy is compromised.
This patch adds a third option, "degraded" mode. This mode can
be selected via the '--activationmode {complete|degraded|partial}'
option to lvchange/vgchange. It can also be set in lvm.conf.
The "degraded" activation mode allows RAID LVs with a sufficient
level of redundancy to activate (e.g. a RAID5 LV with one device
failure, a RAID6 with two device failures, or RAID1 with n-1
failures). RAID LVs with too many device failures are not allowed
to activate - nor are any non-redundant LVs that may have been
affected. This patch also makes the "degraded" mode the default
activation mode.
The degraded activation mode does not yet work in a cluster. A
new cluster lock flag (LCK_DEGRADED_MODE) will need to be created
to make that work. Currently, there is limited space for this
extra flag and I am looking for possible solutions. One possible
solution is to usurp LCK_CONVERT, as it is not used. When the
locking_type is 3, the degraded mode flag simply gets dropped and
the old ("complete") behavior is exhibited.
The --binary option, if used, causes all the binary values reported
in reporting commands to be displayed as "0" or "1" instead of descriptive
literal values (value "unknown" is still used for values that could not be
determined).
Also, add report/binary_values_as_numeric lvm.conf option with the same
functionality as the --binary option (the --binary option prevails
if both --binary cmd option and report/binary_values_as_numeric lvm.conf
option is used at the same time). The report/binary_values_as_numeric is
also profilable.
This makes it easier to use and check lvm reporting command output in scripts.
The list of strings is used quite frequently and we'd like to reuse
this simple structure for report selection support too. Make it part
of libdevmapper for general reuse throughout the code.
This also simplifies the LVM code a bit since we don't need to
include and manage lvm-types.h anymore (the string list was the
only structure defined there).
- When defining configuration source, the code now uses separate
CONFIG_PROFILE_COMMAND and CONFIG_PROFILE_METADATA markers
(before, it was just CONFIG_PROFILE that did not make the
difference between the two). This helps when checking the
configuration if it contains correct set of options which
are all in either command-profilable or metadata-profilable
group without mixing these groups together - so it's a firm
distinction. The "command profile" can't contain
"metadata profile" and vice versa! This is strictly checked
and if the settings are mixed, such profile is rejected and
it's not used. So in the end, the CONFIG_PROFILE_COMMAND
set of options and CONFIG_PROFILE_METADATA are mutually exclusive
sets.
- Marking configuration with one or the other marker will also
determine the way these configuration sources are positioned
in the configuration cascade which is now:
CONFIG_STRING -> CONFIG_PROFILE_COMMAND -> CONFIG_PROFILE_METADATA -> CONFIG_FILE/CONFIG_MERGED_FILES
- Marking configuration with one or the other marker will also make
it possible to issue a command context refresh (will be probably
a part of a future patch) if needed for settings in global profile
set. For settings in metadata profile set this is impossible since
we can't refresh cmd context in the middle of reading VG/LV metadata
and for each VG/LV separately because each VG/LV can have a different
metadata profile assinged and it's not possible to change these
settings at this level.
- When command profile is incorrect, it's rejected *and also* the
command exits immediately - the profile *must* be correct for the
command that was run with a profile to be executed. Before this
patch, when the profile was found incorrect, there was just the
warning message and the command continued without profile applied.
But it's more correct to exit immediately in this case.
- When metadata profile is incorrect, we reject it during command
runtime (as we know the profile name from metadata and not early
from command line as it is in case of command profiles) and we
*do continue* with the command as we're in the middle of operation.
Also, the metadata profile is applied directly and on the fly on
find_config_tree_* fn call and even if the metadata profile is
found incorrect, we still need to return the non-profiled value
as found in the other configuration provided or default value.
To exit immediately even in this case, we'd need to refactor
existing find_config_tree_* fns so they can return error. Currently,
these fns return only config values (which end up with default
values in the end if the config is not found).
- To check the profile validity before use to be sure it's correct,
one can use :
lvm dumpconfig --commandprofile/--metadataprofile ProfileName --validate
(the --commandprofile/--metadataprofile for dumpconfig will come
as part of the subsequent patch)
- This patch also adds a reference to --commandprofile and
--metadataprofile in the cmd help string (which was missing before
for the --profile for some commands). We do not mention --profile
now as people should use --commandprofile or --metadataprofile
directly. However, the --profile is still supported for backward
compatibility and it's translated as:
--profile == --metadataprofile for lvcreate, vgcreate, lvchange and vgchange
(as these commands are able to attach profile to metadata)
--profile == --commandprofile for all the other commands
(--metadataprofile is not allowed there as it makes no sense)
- This patch also contains some cleanups to make the code handling
the profiles more readable...
When cmd refresh is called, we need to move any already loaded profiles
to profiles_to_load list which will cause their reload on subsequent
use. In addition to that, we need to take into account any change
in config/profile configuration setting on cmd context refresh
since this setting could be overriden with --config.
Also, when running commands in the shell, we need to remove the
global profile used from the configuration cascade so the profile
is not incorrectly reused next time when the --profile option is
not specified anymore for the next command in the shell.
This bug only affected profile specified by --profile cmd line
arg, not profiles referenced from LVM metadata.
Before, the cft_check_handle used to direct configuration checking
was part of cmd_context. It's better to attach this as part of the
exact config tree against which the check is done. This patch moves
the cft_check_handle out of cmd_context and it attaches it to the
config tree directly as dm_config_tree->custom->config_source->check_handle.
This change makes it easier to track the config tree check results
and provides less space for bugs as the results are directly attached
to the tree and we don't need to be cautious whether the global value
is correct or not (and whether it needs reinitialization) as it was
in the case when the cft_check_handle was part of cmd_context.
When lvm2 command works with clvmd and uses locking in wrong way,
it may 'leak' certain file descriptors in opened (incorrect) state.
dev_cache_exit then destroys memory pool of cached devices, while
_open_devices list in dev-io.c was still referencing them if they
were still opened.
Patch properly calls _close() function to 'self-heal' from this
invalid state, but it will report internal error (so execution
with abort_on_internal_error causes immediate death). On the
normal 'execution', error is only reported, but memory state is
corrected, and linked list is not referencing devices from
released mempool.
For crash see: https://bugzilla.redhat.com/show_bug.cgi?id=1073886
Since commit f12ee43f2e call destroy,
it start to check all VGs are unlocked. However when we become_daemon,
we simply reset locking (since lock is still kept by parent process).
So implement a simple 'reset' flag.
The global/suffix was missing from example lvm.conf but it can
be very useful when using lvm in scripts and now in profiles as well
Let's expose it more.
The devices/cache and devices/cache_dir are evaluated in runtime this way:
- if devices/cache is set, use it
- if devices_cache/dir or devices/cache_file_prefix is set, make up a
path out of that for devices/cache in runtime, taking into account
the LVM_SYSTEM_DIR environment variable if set
- otherwise make up the path out of default which is:
<LVM_SYSTEM_DIR>/<cache_dir>/<cache_file_prefix>.cache
With the runtime defaults, we can encode this easily now. Also, the lvm
dumpconfig can show proper and exact information about this setting then
(the variant that shows default values).
Using mempool is much safer than using the global static variable.
The global variable would be rewritten on each find_config_tree_* call
and we need to be very careful not to get into this problem (we don't
do now, but we can with the patches for "runtime defaults" that will follow).
This patch adds the new cachepool segment type - the first of two
necessary to eventually create 'cache' logical volumes. In addition
to the new segment type, updates to makefiles, configure files, the
lv_segment struct, and some necessary libdevmapper flags.
The cachepool is the LV and corresponding segment type that will hold
all information pertinent to the cache itself - it's size, cachemode,
cache policy, core arguments (like migration_threshold), etc.
There is a problem with the way mirrors have been designed to handle
failures that is resulting in stuck LVM processes and hung I/O. When
mirrors encounter a write failure, they block I/O and notify userspace
to reconfigure the mirror to remove failed devices. This process is
open to a couple races:
1) Any LVM process other than the one that is meant to deal with the
mirror failure can attempt to read the mirror, fail, and block other
LVM commands (including the repair command) from proceeding due to
holding a lock on the volume group.
2) If there are multiple mirrors that suffer a failure in the same
volume group, a repair can block while attempting to read the LVM
label from one mirror while trying to repair the other.
Mitigation of these races has been attempted by disallowing label reading
of mirrors that are either suspended or are indicated as blocking by
the kernel. While this has closed the window of opportunity for hitting
the above problems considerably, it hasn't closed it completely. This is
because it is still possible to start an LVM command, read the status of
the mirror as healthy, and then perform the read for the label at the
moment after a the failure is discovered by the kernel.
I can see two solutions to this problem:
1) Allow users to configure whether mirrors can be candidates for LVM
labels (i.e. whether PVs can be created on mirror LVs). If the user
chooses to allow label scanning of mirror LVs, it will be at the expense
of a possible hang in I/O or LVM processes.
2) Instrument a way to allow asynchronous label reading - allowing
blocked label reads to be ignored while continuing to process the LVM
command. This would action would allow LVM commands to continue even
though they would have otherwise blocked trying to read a mirror. They
can then release their lock and allow a repair command to commence. In
the event of #2 above, the repair command already in progress can continue
and repair the failed mirror.
This patch brings solution #1. If solution #2 is developed later on, the
configuration option created in #1 can be negated - allowing mirrors to
be scanned for labels by default once again.
Accept --ignoreskippedcluster with pvs, vgs, lvs, pvdisplay, vgdisplay,
lvdisplay, vgchange and lvchange to avoid the 'Skipping clustered
VG' errors when requesting information about a clustered VG
without using clustered locking and still exit with success.
The messages can still be seen with -v.
- null_fd resource leak on error path in _reopen_fd_null fn
- dead code in verify_message in clvmd code
- dead code in _init_filter_components in toolcontext code
- null dereference in dm_prepare_selinux_context on error path if
setfscreatecon fails while resetting SELinux context
Split out the partitioned device filter that needs to open the device
and move the multipath filter in front of it.
When a device is multipathed, sending I/O to the underlying paths may
cause problems, the most obvious being I/O errors visible to lvm if a
path is down.
Revert the incorrect <backtrace> messages added when a device doesn't
pass a filter.
Log each filter initialisation to show sequence.
Avoid duplicate 'Using $device' debug messages.
