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Allow using caching with VDO.
User can either cache a single vdopool or
a vdo LV - difference when the caching is put-in depends on a use-case
and it's upto user to decide which kind of speed is expected.
and "cachepool" to refer to a cache on a cache pool object.
The problem was that the --cachepool option was being used
to refer to both a cache pool object, and to a standard LV
used for caching. This could be somewhat confusing, and it
made it less clear when each kind would be used. By
separating them, it's clear when a cachepool or a cachevol
should be used.
Previously:
- lvm would use the cache pool approach when the user passed
a cache-pool LV to the --cachepool option.
- lvm would use the cache vol approach when the user passed
a standard LV in the --cachepool option.
Now:
- lvm will always use the cache pool approach when the user
uses the --cachepool option.
- lvm will always use the cache vol approach when the user
uses the --cachevol option.
If a single, standard LV is specified as the cache, use
it directly instead of converting it into a cache-pool
object with two separate LVs (for data and metadata).
With a single LV as the cache, lvm will use blocks at the
beginning for metadata, and the rest for data. Separate
dm linear devices are set up to point at the metadata and
data areas of the LV. These dm devs are given to the
dm-cache target to use.
The single LV cache cannot be resized without recreating it.
If the --poolmetadata option is used to specify an LV for
metadata, then a cache pool will be created (with separate
LVs for data and metadata.)
Usage:
$ lvcreate -n main -L 128M vg /dev/loop0
$ lvcreate -n fast -L 64M vg /dev/loop1
$ lvs -a vg
LV VG Attr LSize Type Devices
main vg -wi-a----- 128.00m linear /dev/loop0(0)
fast vg -wi-a----- 64.00m linear /dev/loop1(0)
$ lvconvert --type cache --cachepool fast vg/main
$ lvs -a vg
LV VG Attr LSize Origin Pool Type Devices
[fast] vg Cwi---C--- 64.00m linear /dev/loop1(0)
main vg Cwi---C--- 128.00m [main_corig] [fast] cache main_corig(0)
[main_corig] vg owi---C--- 128.00m linear /dev/loop0(0)
$ lvchange -ay vg/main
$ dmsetup ls
vg-fast_cdata (253:4)
vg-fast_cmeta (253:5)
vg-main_corig (253:6)
vg-main (253:24)
vg-fast (253:3)
$ dmsetup table
vg-fast_cdata: 0 98304 linear 253:3 32768
vg-fast_cmeta: 0 32768 linear 253:3 0
vg-main_corig: 0 262144 linear 7:0 2048
vg-main: 0 262144 cache 253:5 253:4 253:6 128 2 metadata2 writethrough mq 0
vg-fast: 0 131072 linear 7:1 2048
$ lvchange -an vg/min
$ lvconvert --splitcache vg/main
$ lvs -a vg
LV VG Attr LSize Type Devices
fast vg -wi------- 64.00m linear /dev/loop1(0)
main vg -wi------- 128.00m linear /dev/loop0(0)
Different flavors of activate_lv() and lv_is_active()
which are meaningful in a clustered VG can be eliminated
and replaced with whatever that flavor already falls back
to in a local VG.
e.g. lv_is_active_exclusive_locally() is distinct from
lv_is_active() in a clustered VG, but in a local VG they
are equivalent. So, all instances of the variant are
replaced with the basic local equivalent.
For local VGs, the same behavior remains as before.
For shared VGs, lvmlockd was written with the explicit
requirement of local behavior from these functions
(lvmlockd requires locking_type 1), so the behavior
in shared VGs also remains the same.
This minor patch fixes grammar in a few messages which get
printed to users. It also fixes the same grammar mistake in
several comments.
Signed-off-by: Rick Elrod <relrod@redhat.com>
--
As we start refactoring the code to break dependencies (see doc/refactoring.txt),
I want us to use full paths in the includes (eg, #include "base/data-struct/list.h").
This makes it more obvious when we're breaking abstraction boundaries, eg, including a file in
metadata/ from base/
Only policy 'smq' is meant to be used with format version 2.
Code used to let pass 'mq' policy also with format 2. But 'mq'
is obsoloted wth smq and kernel currently matches it. But this
is incompatible with older original mq logic - so disallow creation
of this rather useless combination.
If componet devices could be activated alone, ensure they are not breaking
common commands.
TODO: mostly likely this is not a definite list of all needed checks
and more will come later.
Use properly exclusive activation when reactivating origin after
snapshot merge (since origin must have been previously also exlusively
activated).
Same applies when converting volumes to thin-pool or cache.
Previously used 'only' local activation incorrectly allowed local
activation of some targets (i.e. raid) - thus 'leaking' chance to
activate same device on another node - which can be a problem
for device types like raid.
In some cases the message could be slightly misleading so use
here rather conditional.
TODO:
In future we may possibly further tune the message in case we are
certain the level of redundancy protection has not been reduced.
Basically reverting commit 58a9f88b8c.
We can use origin_only in case we are snapshot's origin,
as we do support this stack.
So when we are 'uncaching' origin+snaps - we do need to reload only
origin and we do not need to play with snaps.
Since cache LV can be a stacked device, there is no real reason
trying to use slight optimised tree for origin_only cache reload
(it could be even wrongly implemented in this case).
We can easily go with stardard tree load here.
When user runs command like 'lvconvert --splitcache' the operation
might be actually either slow or not making any progress in kernel,
so lets give user a chance to abort such operation.
When user press 'Ctrl+C' device table is restored to pre-flushing state.
As now we can properly recognize all paramerters for pool creation,
we may drop PASS_ARG_ defines and rely on '_UNSELECTED' or 0 entries
as being those without user given args.
When setting are not given on command line - 'update' function
fill them from profiles or configuration. For this 'profile' arg
was needed to be passed around and since 'VG' itself is not needed,
it's been all replaced with 'cmd, profile, extents_size' args.
Fix missing reset of '*settings' pointer when no args were given.
Handle cache_chunk settings like all other settings, so it is properly
updated only with non-zero settings and the existing cache-pool
chunk_size is not being reconfigured.
User can specify metadata profile which stores important cache
geometry data for easy configuration.
Fix missing support for getting chunk_size, cache_mode, cache_policy
for a cache/cache pools volumes from configuration or metadata profile.
When we need to clear dirty cache content of cached LV, there
is table reload which usually is shortly followed by next metadata
change. However udev can't (as of now) process udev event
while device is 'suspended'.
So whenever sequence of 'suspend/resume/suspend' is needed,
we need to wait first for finishing of 'resume' processing before
starting next 'suspend'. Otherwise there is 'race' danger of triggering
unwantend umount by systemd as such event will trigger
SYSTEMD_READY=0 state for a moment for such changed device.
Such race is pretty ugly to trace so we may need to review more
sequencies for missing 'sync'.
(Other option is to enhnace 'udev' rules processing to avoid
such dramatic actions to be happening for suspended devices).
Add this functionality to lvconvert:
'lvconvert --thin cachedLV --thinpool vg/poll'
Converts cachedLV to external origin (which will be read-only).
New thin volume is created in thinpool LV and it's using external
origin as source for unprovisioned chunks.
This conversion happens online (while volume is in use).
Thin LV remains fully writable.
Cached external origin no longer could be written so cache will be used
ONLY for read operations. For this limitation we require cache mode
to be writethrough (as writeback cannot write to read-only volumes).
When thinLV is later removed cached external origin is again
fully usable, just note, LV remain in 'read-only' mode.
When read-write is needed, 'lvchange -prw' has to be used.
Single external origin could be user by multiple thinLV in
multiple differen thin pool.
To be ready to show status of cache volume, call the status
with layer. Layer is automatically detected in this case when
cache volume is used in 'layered' form (needs -real suffix).
Avoid printing misleading message about single dirty block.
Instead properly detect condition where the 'cleaner' policy
needs to be installed without 'overloading' dirty variable.
Also print warning if we would be clearing read-only volume.
(it really shouldn't happen).
Introduce 'hard limit' for max number of cache chunks.
When cache target operates with too many chunks (>10e6).
When user is aware of related possible troubles he
may increase the limit in lvm.conf.
Also verbosely inform user about possible solution.
Code works for both lvcreate and lvconvert.
Lvconvert fully supports change of chunk_size when caching LV
(and validates for compatible settings).
Add support for active cache LV.
Handle --cachemode args validation during command line processing.
Rework some lvm2 internal to use lvm2 defined CACHE_MODE enums
indepently on libdm defines and use enum around the code instead
of passing and comparing strings.
