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The common lv_origin_lv fn avoids code duplication and also
the reporting part now uses _lvname_disp and _uuid_disp to display
name and uuid respectively, including brackets for the name if the
dev is invisible.
The common lv_convert_lv fn avoids code duplication and also
the reporting part now uses _lvname_disp and _uuid_disp to display
name and uuid respectively, including brackets for the name if the
dev is invisible.
Use common _lvname_disp to report lv_parent. The _lvname_disp
takes care of properly marking LVs which are not visible - such
LVs are always enclosed in brackets when reported within any
other field.
For example, thin pool over RAID.
Before:
$ lvs -a -o name,lv_parent,data_lv,metadata_lv vg
LV Parent Data Meta
cache_pool [cache_pool_tdata] [cache_pool_tmeta]
[cache_pool_tdata] cache_pool
[cache_pool_tdata_rimage_0] cache_pool_tdata
[cache_pool_tdata_rimage_1] cache_pool_tdata
[cache_pool_tdata_rmeta_0] cache_pool_tdata
[cache_pool_tdata_rmeta_1] cache_pool_tdata
[cache_pool_tmeta] cache_pool
[cache_pool_tmeta_rimage_0] cache_pool_tmeta
[cache_pool_tmeta_rimage_1] cache_pool_tmeta
[cache_pool_tmeta_rmeta_0] cache_pool_tmeta
[cache_pool_tmeta_rmeta_1] cache_pool_tmeta
[lvol0_pmspare]
With this patch applied:
$ lvs -a -o name,lv_parent,data_lv,metadata_lv vg
LV Parent Data Meta
cache_pool [cache_pool_tdata] [cache_pool_tmeta]
[cache_pool_tdata] cache_pool
[cache_pool_tdata_rimage_0] [cache_pool_tdata]
[cache_pool_tdata_rimage_1] [cache_pool_tdata]
[cache_pool_tdata_rmeta_0] [cache_pool_tdata]
[cache_pool_tdata_rmeta_1] [cache_pool_tdata]
[cache_pool_tmeta] cache_pool
[cache_pool_tmeta_rimage_0] [cache_pool_tmeta]
[cache_pool_tmeta_rimage_1] [cache_pool_tmeta]
[cache_pool_tmeta_rmeta_0] [cache_pool_tmeta]
[cache_pool_tmeta_rmeta_1] [cache_pool_tmeta]
[lvol0_pmspare]
Do not mix dm_report_field_set_value and _field_set_value and
use single function call throughout for clarity. The same applies
for dm_report_field_string and _string_disp.
Fix regression caused by commit c2d4330f27
which removed the dm_pool_strdup for the cache policy name in
_cache_policy_disp report function.
This regression was hit with buffered reporting only (which is
used by default). The reason is that for buffered reporting, we're
iterating over LVs in VG (process_each_lv) while gathering
all the information that is needed for the report. In this case,
the LV's cache policy name has not been duped, but only the pointer
to the original VG buffer was stored. When the LV iteration finished,
the VG buffer was freed and any report to output called later
(dm_report_output call) accessed already freed VG data.
This didn't appear if unbuffered reporting was used (--unbuffered)
because in this case, the data were reported to output as
soon as they were processed, hence it was reported to output
before the VG data was freed.
We already have pv_count to report number of PVs that a VG has based
on metadata.
This patch exposes the information about how many of these PVs are
missing which is also useful information for a VG. Wwe could count
the sum of pv_missing reporting fields for each PV in the VG before,
but the new field is practical when reporting VG as a whole and there's
no need to process each PV from VG alone.
Add metadata_devices and seg_metadata_le_ranges report fields.
Currently only defined for raid, but should probably be extended
to all other segment types that don't report all their device
usage in the 'devices' field.
Since cache-pool actualy keeps info about caching,
display this info for cache-pool LV as well
(matches info for cache LV when cache-pool is asociated with it).
Change logic and naming of some internal API functions.
cache_set_mode() and cache_set_policy() both take segment.
cache mode is now correctly 'masked-in'.
If the passed segment is 'cache' segment - it will automatically
try to find 'defaults' according to profiles if the are NOT
specified on command line or they are NOT already set for cache-pool.
These defaults are never set for cache-pool.
Recognize date and time specification within selection criteria
that is formulated in a more free-form way besides to the original
basic YYYY-MM-DD HH:MM format that libdevmapper supports.
Currently, this free-form format is recognized for lv_time field.
Users are able to use expressions from this set:
- weekday names ("Sunday" - "Saturday" or abbreviated as "Sun" - "Sat")
- labels for points in time ("noon", "midnight")
- labels for a day relative to current day ("today", "yesterday")
- points back in time with relative offset from today (N is a number)
( "N" "seconds"/"minutes"/"hours"/"days"/"weeks"/"years" "ago")
( "N" "secs"/"mins"/"hrs" ... "ago")
( "N" "s"/"m"/"h" ... "ago")
- time specification either in hh:mm:ss format or with AM/PM suffixes
- month names ("January" - "December" or abbreviated as "Jan" - "Dec")
For example:
$ date
Fri Jul 3 10:11:13 CEST 2015
$ lvmconfig --type full report/time_format
time_format="%a %Y-%m-%d %T %z %Z [%s]"
$ lvs
LV VG Time
lvol0 vg Fri 2014-08-22 21:25:41 +0200 CEST [1408735541]
lvol2 vg Sun 2015-04-26 14:52:20 +0200 CEST [1430052740]
root fedora Wed 2015-05-27 08:09:21 +0200 CEST [1432706961]
swap fedora Wed 2015-05-27 08:09:21 +0200 CEST [1432706961]
lvol1 vg Tue 2015-06-30 03:25:43 +0200 CEST [1435627543]
lvol3 vg Tue 2015-06-30 14:52:23 +0200 CEST [1435668743]
lvol6 vg Wed 2015-07-01 13:35:56 +0200 CEST [1435750556]
lvol4 vg Thu 2015-07-02 12:12:02 +0200 CEST [1435831922]
lvol5 vg Thu 2015-07-02 14:30:32 +0200 CEST [1435840232]
$ lvs -S 'time=yesterday'
LV VG Time
lvol4 vg Thu 2015-07-02 12:12:02 +0200 CEST [1435831922]
lvol5 vg Thu 2015-07-02 14:30:32 +0200 CEST [1435840232]
$ lvs -S 'time since "June 30"'
LV VG Time
lvol1 vg Tue 2015-06-30 03:25:43 +0200 CEST [1435627543]
lvol3 vg Tue 2015-06-30 14:52:23 +0200 CEST [1435668743]
lvol6 vg Wed 2015-07-01 13:35:56 +0200 CEST [1435750556]
lvol4 vg Thu 2015-07-02 12:12:02 +0200 CEST [1435831922]
lvol5 vg Thu 2015-07-02 14:30:32 +0200 CEST [1435840232]
$ lvs -S 'time since "noon June 30"'
LV VG Time
lvol3 vg Tue 2015-06-30 14:52:23 +0200 CEST [1435668743]
lvol6 vg Wed 2015-07-01 13:35:56 +0200 CEST [1435750556]
lvol4 vg Thu 2015-07-02 12:12:02 +0200 CEST [1435831922]
lvol5 vg Thu 2015-07-02 14:30:32 +0200 CEST [1435840232]
$ lvs -S 'time since "2 July 9AM"'
LV VG Time
lvol4 vg Thu 2015-07-02 12:12:02 +0200 CEST [1435831922]
lvol5 vg Thu 2015-07-02 14:30:32 +0200 CEST [1435840232]
$ lvs -S 'time since "2 July 1PM"'
LV VG Time
lvol5 vg Thu 2015-07-02 14:30:32 +0200 CEST [1435840232]
...and so on.
Wire the dm_report_reserved_handler instance call in reporting/selection
infrastructure to handle reserved value actions (currently only
DM_REPORT_RESERVED_PARSE_FUZZY_NAME and DM_REPORT_RESERVED_GET_DYNAMIC_VALUE
actions).
With fuzzy names we mean the names for which it's hard or even impossible
to enumerate all possible variations of the name - the name needs to
be evaluated. An example of fuzzy name is a name which has a base
(substring) which matches and it can contain arbitrary variations
around this base. We can cover human language better with fuzzy
names as people may use several different names (or sentences) to
denote the same thing.
With dynamic values we mean the values which are not constants
and they need to be evaluated in runtime. An example of dynamic
value is a value which depends on current system state (e.g. time,
current configuration or any other state which may change and it
needs runtime evaluation).
There's a handler that can be registered with reporting/selection
using dm_report_reserved_handler instance. This is a central point
in which the computation/evaluation happens when processing reserved
values. Currently, there are two actions declared:
DM_REPORT_RESERVED_PARSE_FUZZY_NAME
(translates fuzzy name into canonical name)
DM_REPORT_RESERVED_GET_DYNAMIC_VALUE
(gets value for canonical name)
The handler is then registered as value in struct
dm_report_reserved_value (see explaining comments besided
the struct dm_report_reserved_value in libdevmapper.h).
Also, this patch provides support for simple caching of values
used during report/selection via dm_report_value_cache_{set,get}.
This is supposed to be used mainly in the dm_report_reserved_handler
instances to save values among calls so all the handler calls work
with the same base value used in computation/evaluation and/or
possibly to save resources if the evaluation is more time-consuming.
The cache is attached to the dm_report handle and so the cache is
dropped one dm_report is dropped.
This patch adds support for time values used in reporting fields.
The raw values are always stored as number of seconds since epoch.
The support that comes with this patch is the basic one which allows
only for recognition of strictly formatted date and time in selection
criteria (the format follows a subset of formats defined by ISO 8601):
date time timezone
date:
YYYY-MM-DD (or shortly YYYYMMDD)
YYYY-MM (shortly YYYYMM), auto DD=1
YYYY, auto MM=01 and DD=01
time:
hh:mm:ss (or shortly hhmmss)
hh:mm (or shortly hhmm), auto ss=0
hh (or shortly hh), auto mm=0, auto ss=0
timezone (always with + or - sign):
+hh:mm or -hh:mm (or shortly +hhmm or -hhmm)
+hh or -hh
Or directly the time (number of seconds) since Epoch (1970-01-01 00:00:00 UTC)
when the number value is prefixed by "@":
@number_of_seconds_since_epoch
This patch also adds aliases for comparison operators
used together with time values which are more intuitive
to use:
since (as alias for >=)
after (as alias for >)
until (as alias for <=)
before (as alias for <)
For example:
$ lvmconfig --type full report/time_format
time_format="%Y-%m-%d %T %z %Z [%s]"
$ lvs -o name,time vg
LV Time
lvol0 2015-06-28 21:25:41 +0200 CEST [1435519541]
lvol1 2015-06-30 03:25:43 +0200 CEST [1435627543]
lvol2 2015-04-26 14:52:20 +0200 CEST [1430052740]
lvol3 2015-06-30 14:52:23 +0200 CEST [1435668743]
$ lvs vg -o name,time -S 'time since "2015-04-26 15:00" && time until "2015-06-30"'
LV Time
lvol0 2015-06-28 21:25:41 +0200 CEST [1435519541]
lvol1 2015-06-30 03:25:43 +0200 CEST [1435627543]
lvol3 2015-06-30 14:52:23 +0200 CEST [1435668743]
$ lvs vg -o name,time -S 'time since "2015-04-26 15:00" && time until "2015-06-30 6:00"'
LV Time
lvol0 2015-06-28 21:25:41 +0200 CEST [1435519541]
lvol1 2015-06-30 03:25:43 +0200 CEST [1435627543]
$ lvs vg -o name,time -S 'time since @1435519541'
LV Time
lvol0 2015-06-28 21:25:41 +0200 CEST [1435519541]
lvol1 2015-06-30 03:25:43 +0200 CEST [1435627543]
lvol3 2015-06-30 14:52:23 +0200 CEST [1435668743]
This is basic time recognition support that is directly a part of
libdevmapper. Recognition of more free-form expressions will be a
part of subsequent patches.
This patch allows for registration and recognition of reserved
values which are ranges, so they're composed of two values actually
to denote the lower and upper bound for the range (stored as an array
with exactly two items to define the boundaries).
Also, this patch allows for flagging reserved values as named-only
which means that such values are not strictly reserved. The strictly
reserved values are reserved values as used before this patch.
Distinction between strictly-reserved and named-only values
is clearly visible with comparisons. Normally, strictly reserved
value is not accounted for if we do "greater than" or "lower than"
comparisons, for example:
1 2 3 ....
|
abc
- we have "abc" as reserved value for field with value "2"
- the value reported for the field is "abc" (or "2", it doesn't matter here)
- the selection we're processing is -S 'field < abc'
- the result of the selection gives nothing as "abc" is strictly
reserved value (bound to "2") and there's no order defined for
it and it would only match if we directly compared the value
(so -S 'field = abc' would match)
With named-only values, the "abc" is named-only value for "2",
so selection -S 'field < abc" is the same as using -S 'field < 2'.
The "abc" is just an alias for some value so the value or its
assigned name can be used equally in selection criteria.
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
Currently lvm2app properties have the following structure:
typedef struct lvm_property_value {
uint32_t is_settable:1;
uint32_t is_string:1;
uint32_t is_integer:1;
uint32_t is_valid:1;
uint32_t padding:28;
union {
const char *string;
uint64_t integer;
} value;
} lvm_property_value_t;
which assumes that numerical values were in the range of 0 to 2**64-1. However,
some of the properties were 'signed', like LV major/minor numbers and some
reserved values for properties that represent percentages. Thus when the
values were retrieved they were in two's complement notation. So for a -1
major number the API user would get a value of 18446744073709551615. The
API user could cast the returned value to an int64_t to handle this, but that
requires the API developer to look at the source code and determine when it
should be done.
This change modifies the return property structure to:
typedef struct lvm_property_value {
uint32_t is_settable:1;
uint32_t is_string:1;
uint32_t is_integer:1;
uint32_t is_valid:1;
uint32_t is_signed:1;
uint32_t padding:27;
union {
const char *string;
uint64_t integer;
int64_t signed_integer;
} value;
} lvm_property_value_t;
With this addition the API user can interrogate that the value is numerical,
(is_integer = 1) and subsequently check if it's signed (is_signed = 1) too.
If signed, then the API developer should use the union's signed_integer to
avoid casting.
This change maintains backwards compatibility as the structure size remains
unchanged and integer value remains unchanged. Only the additional bit
taken from the pad is utilized.
Bugzilla reference:
https://bugzilla.redhat.com/show_bug.cgi?id=838257
Signed-off-by: Tony Asleson <tasleson@redhat.com>
Show full chain of ancestors and descendants for snapshots
(both thick and thin - in case of thick, the "ancestor" field
is actually equal to "origin" field as snapshots can't be
chained for thick snapshots).
These fields display current state as it is, they do not
display any history! If the snapshot chain is broken in
the middle, we don't report the historical origin (this
is going to be a part of another patch and a different
set of fields or just a switch for existing fields to
show ancestors and descendants with history included).
For example:
(origin --> snapshot)
lvol1 --> lvol2 --> lvol3 --> lvol4
\
--> lvol5 --> lvol6 --> lvol7 --> lvol8
$ lvs -o name,pool_lv,origin,ancestors,descendants vg
LV Pool Origin Ancestors Descendants
lvol1 pool lvol2,lvol3,lvol4,lvol5,lvol6,lvol7,lvol8
lvol2 pool lvol1 lvol1 lvol3,lvol4,lvol5,lvol6,lvol7,lvol8
lvol3 pool lvol2 lvol2,lvol1 lvol4
lvol4 pool lvol3 lvol3,lvol2,lvol1
lvol5 pool lvol2 lvol2,lvol1 lvol6,lvol7,lvol8
lvol6 pool lvol5 lvol5,lvol2,lvol1 lvol7,lvol8
lvol7 pool lvol6 lvol6,lvol5,lvol2,lvol1 lvol8
lvol8 pool lvol7 lvol7,lvol6,lvol5,lvol2,lvol1
Scenario:
$ vgs -o+vg_mda_copies
VG #PV #LV #SN Attr VSize VFree #VMdaCps
fedora 1 2 0 wz--n- 9.51g 0 unmanaged
vg 16 9 0 wz--n- 1.94g 1.83g 2
$ lvs -o+read_ahead vg/lvol6 vg/lvol7
LV VG Attr LSize Pool Origin Data% Rahead
lvol6 vg Vwi-a-tz-- 1.00g pool lvol5 0.00 auto
lvol7 vg Vwi---tz-k 1.00g pool lvol6 256.00k
Before this patch:
$vgs -o vg_name,vg_mda_copies -S 'vg_mda_copies < unmanaged'
VG #VMdaCps
vg 2
Problem:
Reserved values can be only used with exact match = or !=, not <,<=,>,>=.
In the example above, the "unamanaged" is internally represented as
18446744073709551615, but this should be ignored while not comparing
field directly with "unmanaged" reserved name with = or !=. Users
should not be aware of this internal mapping of the reserved value
name to its internal value and hence it doesn't make sense for such
reserved value to take place in results of <,<=,> and >=.
There's no order defined for reserved values!!! It's a special
*reserved* value that is taken out of the usual value range
of that type.
This is very similar to what we have already fixed with
2f7f6932dc, but it's the other way round
now - we're using reserved value name in selection criteria now
(in the patch 2f7f693, we had concrete value and we compared it
with the reserved value). So this patch completes patch 2f7f693.
This patch also fixes this problem:
$ lvs -o+read_ahead vg/lvol6 vg/lvol7 -S 'read_ahead > 32k'
LV VG Attr LSize Pool Origin Data% Rahead
lvol6 vg Vwi-a-tz-- 1.00g pool lvol5 0.00 auto
lvol7 vg Vwi---tz-k 1.00g pool lvol6 256.00k
Problem:
In the example above, the internal reserved value "auto" is in the
range of selection "> 32k" - it shouldn't match as well. Here the
"auto" is internally represented as MAX_DBL and of course, numerically,
MAX_DBL > 256k. But for users, the reserved value should be uncomparable
to any number so the mapping of the reserved value name to its interna
value is transparent to users. Again, there's no order defined for
reserved values and hence it should never match if using <,<=,>,>=
operators.
This is actually exactly the same problem as already described in
2f7f6932dc, but that patch failed for
size field types because of incorrect internal representation used.
With this patch applied, both problematic scenarios mentioned
above are fixed now:
$ vgs -o vg_name,vg_mda_copies -S 'vg_mda_copies < unmanaged'
(blank)
$ lvs -o+read_ahead vg/lvol6 vg/lvol7 -S 'read_ahead > 32k'
LV VG Attr LSize Pool Origin Rahead
lvol7 vg Vwi---tz-k 1.00g pool lvol6 256.00k
The seg_monitor did not display monitored status for thick snapshots
and mirrors (with mirror log *not* mirrored). The seg monitor did work
correctly even before for other segtypes - thins and raids.
Before (mirrors and snapshots, only mirrors with mirrored log properly displayed monitoring status):
[0] f21/~ # lvs -a -o lv_name,lv_layout,lv_role,seg_monitor vg
LV Layout Role Monitor
mirror mirror public
[mirror_mimage_0] linear private,mirror,image
[mirror_mimage_1] linear private,mirror,image
[mirror_mlog] linear private,mirror,log
mirror_with_mirror_log mirror public monitored
[mirror_with_mirror_log_mimage_0] linear private,mirror,image
[mirror_with_mirror_log_mimage_1] linear private,mirror,image
[mirror_with_mirror_log_mlog] mirror private,mirror,log monitored
[mirror_with_mirror_log_mlog_mimage_0] linear private,mirror,image
[mirror_with_mirror_log_mlog_mimage_1] linear private,mirror,image
thick_origin linear public,origin,thickorigin
thick_snapshot linear public,snapshot,thicksnapshot
With this patch applied (monitoring status displayed for all mirrors and snapshots):
[0] f21/~ # lvs -a -o lv_name,lv_layout,lv_role,seg_monitor vg
LV Layout Role Monitor
mirror mirror public monitored
[mirror_mimage_0] linear private,mirror,image
[mirror_mimage_1] linear private,mirror,image
[mirror_mlog] linear private,mirror,log
mirror_with_mirror_log mirror public monitored
[mirror_with_mirror_log_mimage_0] linear private,mirror,image
[mirror_with_mirror_log_mimage_1] linear private,mirror,image
[mirror_with_mirror_log_mlog] mirror private,mirror,log monitored
[mirror_with_mirror_log_mlog_mimage_0] linear private,mirror,image
[mirror_with_mirror_log_mlog_mimage_1] linear private,mirror,image
thick_origin linear public,origin,thickorigin
thick_snapshot linear public,snapshot,thicksnapshot monitored
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.
The new "report_init_for_selection" is just a wrapper over
dm_report_init_with_selection that initializes reporting for selection
only. This means we're not going to do the actual reporting to output
for display and as such we intialize reporting as if no fields are reported
or sorted. The only fields "reported" are taken from the selection criteria
string and all such fields are marked as hidden automatically (FLD_HIDDEN flag).
These fields are used solely for selection criteria matching.
Also, modify existing report_object function that was used for reporting to
output for display. Now, it can either cause reporting to output or reporting
for selection only. The selection result is stored in struct selection_handle's
"selected" variable which can be handled further by any report_object caller.
Rename original lv_error_when_full field to lv_when_full and also
convert it from binary field to string field displaying three
possible values: "error", "queueu" or "" (blank for undefined).
$ lvs vg/pool vg/pool1 vg/linear_lv -o+lv_when_full
LV VG Attr LSize Data% Meta% WhenFull
linear_lv vg -wi-a----- 4.00m
pool vg twi-aotz-- 4.00m 0.00 0.98 queue
pool1 vg twi-a-tz-- 4.00m 0.00 0.88 error
For -S|--select these synonyms are recognized:
"error" -> "error when full", "error if no space"
"queue" -> "queue when full", "queue if no space"
"" -> "undefined"
Add separate LVSINFOSTATUS field type for fields which display both
dm info-like and dm status-like information.
The internal interface is there with the introduction of LVSSTATUS
field type which can cope with the combination of LVSSTATUS
and LVSINFO field types (several fields).
However, till now, we considered that *single* field can display
either LVSINFO or LVSSTATUS, but not both at the same time.
Till now, we haven't had single field which needs both - hence
add LVSINFOSTATUS field type for such fields as we currently
need this for the lv_attr field which requires combination of
info and status.
This patch just adds interface for an ability to register such fields
(the code that copes with this is already in).
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.
Support error_if_no_space feature for thin pools.
Report more info about thinpool status:
(out_of_data (D), metadata_read_only (M), failed (F) also as health
attribute.)
API for seg reporting is breaking internal lvm coding - it cannot
use vgmem mem pool for allocation of reported value.
So use separate pool instead of 'vgmem' for non vg related allocations
Add consts for many function params - but still many other are left
for now as non-const - needs deeper level of change even on libdm side.
Since GET_FIELD_RESERVED_VALUE always returns a pointer, don't reference
it with "&" when used - we already have that pointer value (this is an
addendum to recent commit 028ff30947).
Only GET_TYPE_RESERVED_VALUE needs to be referenced with "&" as it
returns directly the value of that type.
We have to use empty list, not NULL if we want to denote that the list
has no items. Otherwise, the code further can segfault as it expects
there's always a sane value (= some list), including empty list,
but never NULL.
Use helper macros to handle reserved values and also define "undefined"
reserved value as:
FIELD_RESERVED_VALUE(cache_policy, cache_policy_undef, "", "", "undefined")
Which means:
- print "" if the cache_policy value is undefined (the first name for this reserved value is "")
- recognize "undefined" reserved name as synonym to ""
(so statements like "lvs -S cache_policy=undefined" are still recognized)
Avoid making a copy of the keyword which is already registered in
values.h for "unmanaged" (vg_mda_copies field) and "auto" reserved
value (lv_read_ahead field). Also use helper macros to handle these
reserved - this is the correct approach - just do not copy the same
thing again and do not mix it! The GET_FIELD_RESERVED_VALUE and
GET_FIRST_RESERVED_NAME macros guarantees this - use it!
In addition to that, rename reserved values:
vg_mda_copies --> vg_mda_copies_unmanaged
lv_read_ahead --> lv_read_ahead_auto
So the field reserved values follows this scheme:
"<field_name>_<reserved_value_name>".
The same applies for type reserved values with this scheme:
"<report type name in lowercase>_<reserved_value_name>"
Add a comment about this scheme for others to follow as well
when adding new fields and their reserved values. This makes
it a bit easier to read the code then.
