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Historical LV is valid as long as there is at least one live LV among
its ancestors. If we find any invalid (dangling) historical LVs, remove
them automatically.
The vg_strip_outdated_historical_lvs iterates over the list of historical LVs
we have and it shoots down the ones which are outdated.
Configuration hook to set the timeout will be in subsequent patch.
The metadata/record_lvs_history is global switch which enables or
disables recording historical LVs in metadata.
If both metadata/record_lvs_history=1 lvm.conf option and
--nohistory command switch is used at the same time, the
--nohistory prevails.
Report proper values for historical LVs in lv_layout and lv_role fields.
Any historical LV doesn't have any layout anymore and the role is "history".
For example:
$ lvs -H -o name,lv_attr,lv_layout,lv_role vg/-lvol1
LV Attr Layout Role
-lvol1 ----h----- none public,history
The lv_full_ancestors reporting field is just like the existing
lv_ancestors field but it also takes into account any history and
indirect relations recorded.
All names for historical LVs are prefixed with '-' character to make clear
difference between live and historical LVs. The '-' can't be set by users
for live LV names during lvcreate hence we never get into a conflict with
the names that user defines for live LVs.
The lv_historical reporting field is a simple binary field that reports
whether an LV is historical one ("historical" value or value of "1" displayed)
or not (blank string "" or value of "0" displayed).
When processing LVs in a VG and when the -H|--history switch is used,
make process_each_lv_in_vg to iterate over historical volumes too.
For each historical LV, we use dummy struct logical_volume instance with
the "this_glv" reference set to a wrapper over proper struct
historical_logical_volume representation. This makes it possible to process
historical LVs just like normal live LVs (though a dummy one without any
segments and all the other fields zeroed and blank) and it also allows
for using all historical LV related information via lv->this_glv->historical
reference.
One can use a simple call to lv_is_historical to make a difference between
live and historical LV in all the code that is called by process_each_* fns.
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.
Add support for making an interconnection between thin LV segment and
its indirect origin (which may be historical or live LV) - add a new
"indirect_origin" argument to attach_pool_lv function.
Also export historical LVs when exporting LVM2 metadata.
This is list of all historical LVs listed in
"historical_logical_volumes" metadata section with all
the properties exported for each historical LV.
For example, we have this thin snapshot sequence:
lvol1 --> lvol2 --> lvol3
\
--> lvol4
We end up with these metadata:
logical_volume {
...
(lvol1, lvol3 and lvol4 listed here as usual - no change here)
...
}
historical_logical_volumes {
lvol2 {
id = "S0Dw1U-v5sF-LwAb-W9SI-pNOF-Madd-5dxSv5"
creation_time = 1456919613 # 2016-03-02 12:53:33 +0100
removal_time = 1456919620 # 2016-03-02 12:53:40 +0100
origin = "lvol1"
descendants = ["lvol3", "lvol4"]
}
}
By removing lvol1 further, we end up with:
historical_logical_volumes {
lvol2 {
id = "S0Dw1U-v5sF-LwAb-W9SI-pNOF-Madd-5dxSv5"
creation_time = 1456919613 # 2016-03-02 12:53:33 +0100
removal_time = 1456919620 # 2016-03-02 12:53:40 +0100
origin = "-lvol1"
descendants = ["lvol3", "lvol4"]
}
lvol1 {
id = "me0mes-aYnK-nRfT-vNlV-UiR1-GP7r-ojbROr"
creation_time = 1456919608 # 2016-03-02 12:53:28 +0100
removal_time = 1456919767 # 2016-03-02 12:56:07 +0100
}
}
When an LV is being removed, we create an instance of
"struct historical_logical_volume" wrapped up in
"struct generic_logical_volume".
All instances of "struct historical_logical_volume" are then recorded in
"historical_lvs" list which is part of "struct volume_group".
The "historical LV" is then interconnected with "live LVs" to
connect a history chain for the live LV.
The add_glv_to_indirect_glvs is a helper function that registers a
volume represented by struct generic_logical_volume instance ("glv")
as an indirect user of another volume ("origin_glv") and vice versa -
it also registers the other volume ("origin_glv") as indirect_origin
of user volume ("glv").
The remove_glv_from_indirect_glvs does the opposite.
The get_or_create_glv is helper function that retrieves any existing
generic_logical_volume wrapper for the LV. If the wrapper does not exist
yet, it's created.
The get_org_create_glvl is the same as get_or_create_glv but it creates
the glv_list wrapper in addition so it can be added to a list.
Add new structures and new fields in existing structures to support
tracking history of LVs (the LVs which don't exist - the have been
removed already):
- new "struct historical_logical_volume"
This structure keeps information specific to historical LVs
(historical LV is very reduced form of struct logical_volume +
it contains a few specific fields to track historical LV
properties like removal time and connections among other LVs).
- new "struct generic_logical_volume"
Wrapper for "struct historical_logical_volume" and
"struct logical_volume" to make it possible to handle volumes
in uniform way, no matter if it's live or historical one.
- new "struct glv_list"
Wrapper for "struct generic_logical_volume" so it can be
added to a list.
- new "indirect_glvs" field in "struct logical_volume"
List that stores references to all indirect users of this LV - this
interconnects live LV with historical descendant LVs or even live
descendant LVs.
- new "indirect_origin" field in "struct lv_segment"
Reference to indirect origin of this segment - this interconnects
live LV (segment) with historical ancestor.
- new "this_glv" field in "struct logical_volume"
This references an existing generic_logical_volume wrapper for this
LV, if used. It can be NULL if not needed - which means we're not
handling historical LVs at all.
- new "historical_lvs" field in "struct volume group
List of all historical LVs read from VG metadata.
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'.
