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This patch makes the keyword combinations found in "lv_layout" and
"lv_role" much more understandable - there were some ambiguities
for some of the combinations which lead to confusion before.
Now, the scheme used is:
LAYOUTS ("how the LV is laid out"):
===================================
[linear] (all segments have number of stripes = 1)
[striped] (all segments have number of stripes > 1)
[linear,striped] (mixed linear and striped)
raid (raid layout always reported together with raid level, raid layout == image + metadata LVs underneath that make up raid LV)
[raid,raid1]
[raid,raid10]
[raid,raid4]
[raid,raid5] (exact sublayout not specified during creation - default one used - raid5_ls)
[raid,raid5,raid5_ls]
[raid,raid5,raid6_rs]
[raid,raid5,raid5_la]
[raid,raid5,raid5_ra]
[raid6,raid] (exact sublayout not specified during creation - default one used - raid6_zr)
[raid,raid6,raid6_zr]
[raid,raid6,raid6_nc]
[raid,raid6,raid6_ns]
[mirror] (mirror layout == log + image LVs underneath that make up mirror LV)
thin (thin layout always reported together with sublayout)
[thin,sparse] (thin layout == allocated out of thin pool)
[thin,pool] (thin pool layout == data + metadata volumes underneath that make up thin pool LV, not supposed to be used for direct use!!!)
[cache] (cache layout == allocated out of cache pool in conjunction with cache origin)
[cache,pool] (cache pool layout == data + metadata volumes underneath that make up cache pool LV, not supposed to be used for direct use!!!)
[virtual] (virtual layout == not hitting disk underneath, currently this layout denotes only 'zero' device used for origin,thickorigin role)
[unknown] (either error state or missing recognition for such layout)
ROLES ("what's the purpose or use of the LV - what is its role"):
=================================================================
- each LV has either of these two roles at least: [public] (public LV that users may use freely to write their data to)
[public] (public LV that users may use freely to write their data to)
[private] (private LV that LVM maintains; not supposed to be directly used by user to write his data to)
- and then some special-purpose roles in addition to that:
[origin,thickorigin] (origin for thick-style snapshot; "thick" as opposed to "thin")
[origin,multithickorigin] (there are more than 2 thick-style snapshots for this origin)
[origin,thinorigin] (origin for thin snapshot)
[origin,multithinorigin] (there are more than 2 thin snapshots for this origin)
[origin,extorigin] (external origin for thin snapshot)
[origin,multiextoriginl (there are more than 2 thin snapshots using this external origin)
[origin,cacheorigin] (cache origin)
[snapshot,thicksnapshot] (thick-style snapshot; "thick" as opposed to "thin")
[snapshot,thinsnapshot] (thin-style snapshot)
[raid,metadata] (raid metadata LV)
[raid,image] (raid image LV)
[mirror,image] (mirror image LV)
[mirror,log] (mirror log LV)
[pvmove] (pvmove LV)
[thin,pool,data] (thin pool data LV)
[thin,pool,metadata] (thin pool metadata LV)
[cache,pool,data] (cache pool data LV)
[cache,pool,metadata] (cache pool metadata LV)
[pool,spare] (pool spare LV - common role of LV that makes it used for both thin and cache repairs)
The lv_layout and lv_type fields together help with LV identification.
We can do basic identification using the lv_attr field which provides
very condensed view. In contrast to that, the new lv_layout and lv_type
fields provide more detialed information on exact layout and type used
for LVs.
For top-level LVs which are pure types not combined with any
other LV types, the lv_layout value is equal to lv_type value.
For non-top-level LVs which may be combined with other types,
the lv_layout describes the underlying layout used, while the
lv_type describes the use/type/usage of the LV.
These two new fields are both string lists so selection (-S/--select)
criteria can be defined using the list operators easily:
[] for strict matching
{} for subset matching.
For example, let's consider this:
$ lvs -a -o name,vg_name,lv_attr,layout,type
LV VG Attr Layout Type
[lvol1_pmspare] vg ewi------- linear metadata,pool,spare
pool vg twi-a-tz-- pool,thin pool,thin
[pool_tdata] vg rwi-aor--- level10,raid data,pool,thin
[pool_tdata_rimage_0] vg iwi-aor--- linear image,raid
[pool_tdata_rimage_1] vg iwi-aor--- linear image,raid
[pool_tdata_rimage_2] vg iwi-aor--- linear image,raid
[pool_tdata_rimage_3] vg iwi-aor--- linear image,raid
[pool_tdata_rmeta_0] vg ewi-aor--- linear metadata,raid
[pool_tdata_rmeta_1] vg ewi-aor--- linear metadata,raid
[pool_tdata_rmeta_2] vg ewi-aor--- linear metadata,raid
[pool_tdata_rmeta_3] vg ewi-aor--- linear metadata,raid
[pool_tmeta] vg ewi-aor--- level1,raid metadata,pool,thin
[pool_tmeta_rimage_0] vg iwi-aor--- linear image,raid
[pool_tmeta_rimage_1] vg iwi-aor--- linear image,raid
[pool_tmeta_rmeta_0] vg ewi-aor--- linear metadata,raid
[pool_tmeta_rmeta_1] vg ewi-aor--- linear metadata,raid
thin_snap1 vg Vwi---tz-k thin snapshot,thin
thin_snap2 vg Vwi---tz-k thin snapshot,thin
thin_vol1 vg Vwi-a-tz-- thin thin
thin_vol2 vg Vwi-a-tz-- thin multiple,origin,thin
Which is a situation with thin pool, thin volumes and thin snapshots.
We can see internal 'pool_tdata' volume that makes up thin pool has
actually a level10 raid layout and the internal 'pool_tmeta' has
level1 raid layout. Also, we can see that 'thin_snap1' and 'thin_snap2'
are both thin snapshots while 'thin_vol1' is thin origin (having
multiple snapshots).
Such reporting scheme provides much better base for selection criteria
in addition to providing more detailed information, for example:
$ lvs -a -o name,vg_name,lv_attr,layout,type -S 'type=metadata'
LV VG Attr Layout Type
[lvol1_pmspare] vg ewi------- linear metadata,pool,spare
[pool_tdata_rmeta_0] vg ewi-aor--- linear metadata,raid
[pool_tdata_rmeta_1] vg ewi-aor--- linear metadata,raid
[pool_tdata_rmeta_2] vg ewi-aor--- linear metadata,raid
[pool_tdata_rmeta_3] vg ewi-aor--- linear metadata,raid
[pool_tmeta] vg ewi-aor--- level1,raid metadata,pool,thin
[pool_tmeta_rmeta_0] vg ewi-aor--- linear metadata,raid
[pool_tmeta_rmeta_1] vg ewi-aor--- linear metadata,raid
(selected all LVs which are related to metadata of any type)
lvs -a -o name,vg_name,lv_attr,layout,type -S 'type={metadata,thin}'
LV VG Attr Layout Type
[pool_tmeta] vg ewi-aor--- level1,raid metadata,pool,thin
(selected all LVs which hold metadata related to thin)
lvs -a -o name,vg_name,lv_attr,layout,type -S 'type={thin,snapshot}'
LV VG Attr Layout Type
thin_snap1 vg Vwi---tz-k thin snapshot,thin
thin_snap2 vg Vwi---tz-k thin snapshot,thin
(selected all LVs which are thin snapshots)
lvs -a -o name,vg_name,lv_attr,layout,type -S 'layout=raid'
LV VG Attr Layout Type
[pool_tdata] vg rwi-aor--- level10,raid data,pool,thin
[pool_tmeta] vg ewi-aor--- level1,raid metadata,pool,thin
(selected all LVs with raid layout, any raid layout)
lvs -a -o name,vg_name,lv_attr,layout,type -S 'layout={raid,level1}'
LV VG Attr Layout Type
[pool_tmeta] vg ewi-aor--- level1,raid metadata,pool,thin
(selected all LVs with raid level1 layout exactly)
And so on...
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).
The two liblvm functions that return a list of vgnames and vguuids use
cmd->mem to allocate the list. Make it clear to the caller that this
memory will be freed when the LVM handle is freed.
Clean up and clarify the return value of the functions. In the
case of a memory allocation error, add a couple log_errnos to the internal
code, and make it clear that memory allocation returns a NULL pointer.
If there are no VGs in the system, the list returned is an empty list.
Make a note of the fact that currently we return hidden VG names, how
these can be detected (always start with "#"), and that they should
not be used.
Author: Dave Wysochanski <dwysocha@redhat.com>
