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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.
Mark profilable settings with a separate CFG_PROFILABLE_METADATA
flag where the profile can be attached to VG/LV. This makes it possible
to differentiate global command-profilable settings (CFG_PROFILABLE flag)
and contextual metadata-profilable (per VG/LV) settings (CFG_PROFILABLE_METADATA flag).
Before:
thin_disabled_features = ""
Now:
thin_disabled_features = []
Which is a more correct and consistent way of specifying void array
though parses can handle both forms.
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.
Users can create several profiles for how the tools report
the output very easily and then just use
<lvm reporting command> --profile <report_profile_name>
Let's do this the other way round - this makes more logic than commit b995f06.
So let's allow empty values for global/thin_disabled_features where
such an empty value now means "none of this features are disabled".
The global/thin_disabled_features should be marked as having no default
value. Otherwise the output from 'lvm dumpconfig --type default' would
have 'thin_disabled_features=""' which will produce an error message
'Ignoring empty string in config file ...' if such output is feed
back to lvm.
The same as for allocation/thin_pool_chunk_size - the default value
used is just a starting point. The calculation continues using the
properties of the devices actually used.
The allocation/thin_pool_chunk_size is a bit more complex. It's default
value is evaluated in runtime based on selected thin_pool_chunk_size_policy.
But the value is just a starting point. The calculation then continues
with dependency on the properties of the devices used. Which means for
such a default value, we know only the starting value.
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).
Previously, we declared a default value as undefined ("NULL") for
settings which require runtime context to be set first (e.g. settings
for paths that rely on SYSTEM_DIR environment variable or they depend
on any other setting in some way).
If we want to output default values as they are really used in runtime,
we should make it possible to define a default value as function which
is evaluated, not just providing a firm constant value as it was before.
This patch defines simple prototypes for such functions. Also, there's
new helper macros "cfg_runtime" and "cfg_array_runtime" - they provide
exactly the same functionality as the original "cfg" and "cfg_array"
macros when defining the configuration settings in config_settings.h,
but they don't set the constant default value. Instead, they automatically
link the configuration setting definition with one of these functions:
typedef int (*t_fn_CFG_TYPE_BOOL) (struct cmd_context *cmd, struct profile *profile);
typedef int (*t_fn_CFG_TYPE_INT) (struct cmd_context *cmd, struct profile *profile);
typedef float (*t_fn_CFG_TYPE_FLOAT) (struct cmd_context *cmd, struct profile *profile);
typedef const char* (*t_fn_CFG_TYPE_STRING) (struct cmd_context *cmd, struct profile *profile);
typedef const char* (*t_fn_CFG_TYPE_ARRAY) (struct cmd_context *cmd, struct profile *profile);
(The new macros actually set the CFG_DEFAULT_RUNTIME flag properly and
set the default value link to the function accordingly).
Then such configuration setting requires a function of selected type to
be defined. This function has a predefined name:
get_default_<id>
...where the <id> is the id of the setting as defined in
config_settings.h. For example "backup_archive_dir_CFG" if defined
as a setting with default value evaluated in runtime with "cfg_runtime"
will automatically have "get_default_backup_archive_dir_CFG" function
linked to this setting to get the default value.
These settings don't have any default value predefined:
log/file
log/activate_file
global/library_dir
This settings has default value but not yet declared in config_settings.h:
global/locking_library (default is DEFAULT_LOCKING_LIB)
To make "lvm dumpconfig --type default" output to be usable like any
other config, we need to comment out lines that have no default value
defined. Otherwise, we'd have the output with config options
with blank or zero values which is not the same as when the value
is not defined! And such configuration can't be feed into lvm again
without further edits. So let's fix this.
Currently this covers these configuration options exactly:
devices/loopfiles
devices/preferred_names
devices/filter
devices/global_filter
devices/types
allocation/cling_tag_list
global/format_libraries
global/segment_libraries
activation/volume_list
activation/auto_activation_volume_list
activation/read_only_volume_list
activation/mlock_filter
metadata/dirs
metadata/disk_areas
metadata/disk_areas/<disk_area>
metadata/disk_areas/<disk_area>/start_sector
metadata/disk_areas/<disk_area>/size
metadata/disk_areas/<disk_area>/id
tags/<tag>
tags/<tag>/host_list
Cache pools require a data and metadata area (like thin pools). Unlike
thin pool, if 'cache_pool_metadata_require_separate_pvs' is not set to
'1', the metadata and data area will be allocated from the same device.
It is also done in a manner similar to RAID, where a single chunk of
space is allocated and then split to form the metadata and data device -
ensuring that they are together.
The metadata/disk_areas setting was incorrectly registered as
"string" configuration option but it's a section where each area
is defined in its own subsection with "start_sector", "size" and "id"
setting.
This setting is not officialy supported, it's undocumented and it's
used solely for debugging.
Note: At this moment, it does not seem to be working with lvmetad!
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.
Add allocation/thin_pool_chunk_size_calculation lvm.conf
option to select a method for calculating thin pool chunk
sizes and define two possible values - "default" and "performance".
Add internal devtypes reporting command to display built-in recognised
block device types. (The output does not include any additional
types added by a configuration file.)
> lvm devtypes -o help
Device Types Fields
-------------------
devtype_all - All fields in this section.
devtype_name - Name of Device Type exactly as it appears in /proc/devices.
devtype_max_partitions - Maximum number of partitions. (How many device minor numbers get reserved for each device.)
devtype_description - Description of Device Type.
> lvm devtypes
DevType MaxParts Description
aoe 16 ATA over Ethernet
ataraid 16 ATA Raid
bcache 1 bcache block device cache
blkext 1 Extended device partitions
...
Add new configure lvm.conf options for binaries thin_repair
and thin_dump.
Those are part of device-mapper-persistent-data package
and will be used for recovery of thin_pool.
cfg_def_get_path uses a global static var to store the result (for efficiency).
So we need to apply the profile first and then get the path for the config item
when calling find_config_tree_* fns.
Also activation/auto_set_activation is not profilable (at least not now,
maybe later if we need that).
The activation/auto_set_activation_skip enables/disables automatic
adding of the ACTIVATION_SKIP LV flag. By default thin snapshots
are flagged to be skipped during activation.
And by default, the auto_set_activation_skip is enabled.
These settins are customizable by profiles:
allocation/thin_pool_zero
allocation/thin_pool_discards
allocation/thin_pool_chunk_size
activation/thin_pool_autoextend_threshold
activation/thin_pool_autoextend_percent
Besides the classical configuration checks (type checking and
checking whether the item is recognized by lvm tools) for profiles,
do an extra check whether the configuration setting is customizable
by a profile at all. Give a warning message if not.
This patch adds --profile arg to lvm cmds and adds config/profile_dir
configuration setting to select the directory where profiles are stored
By default it's /etc/lvm/profile.
The profiles are added by using new "add_profile" fn and then loaded
using the "load_profile" fn. All profiles are stored in a cmd context
within the new "struct profile_params":
struct profile_params {
const char *dir;
struct profile *global_profile;
struct dm_list profiles_to_load;
struct dm_list profiles;
};
...where "dir" is the directory with profiles, "global_profile" is
the profile that is set globally via the --profile arg (IOW, not
set per VG/LV basis based on metadata record) and the "profiles"
is the list with loaded profiles.
Configuration checking is initiated during config load/processing
(_process_config fn) which is part of the command context
creation/refresh.
This patch also defines 5 types of trees that could be created from
the configuration definition (config_settings.h), the cfg_def_tree_t:
- CFG_DEF_TREE_CURRENT that denotes a tree of all the configuration
nodes that are explicitly defined in lvm.conf/--config
- CFG_DEF_TREE_MISSING that denotes a tree of all missing
configuration nodes for which default valus are used since they're
not explicitly used in lvm.conf/--config
- CFG_DEF_TREE_DEFAULT that denotes a tree of all possible
configuration nodes with default values assigned, no matter what
the actual lvm.conf/--config is
- CFG_DEF_TREE_NEW that denotes a tree of all new configuration nodes
that appeared in given version
- CFG_DEF_TREE_COMPLETE that denotes a tree of the whole configuration
tree that is used in LVM2 (a combination of CFG_DEF_TREE_CURRENT +
CFG_DEF_TREE_MISSING). This is not implemented yet, it will be added
later...
The function that creates the definition tree of given type:
struct dm_config_tree *config_def_create_tree(struct config_def_tree_spec *spec);
Where the "spec" specifies the tree type to be created:
struct config_def_tree_spec {
cfg_def_tree_t type; /* tree type */
uint16_t version; /* tree at this LVM2 version */
int ignoreadvanced; /* do not include advanced configs */
int ignoreunsupported; /* do not include unsupported configs */
};
This tree can be passed to already existing functions that write
the tree on output (like we already do with cmd->cft).
There is a new lvm.conf section called "config" with two new options:
- config/checks which enables/disables checking (enabled by default)
- config/abort_on_errors which enables/disables aborts on any type of
mismatch found in the config (disabled by default)
This file centrally defines all recognized LVM2 configuration
sections and settings. Each item here has its parent, set of
allowed types, default value, brief comment, version the setting
first appeared in and flags that further define the nature of
the configuration setting and its use.
