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Support has many limitations and lots of FIXMEs inside,
however it makes initial task when user creates a separate LV for
thin pool data and thin metadata already usable, so let's enable
it for testing.
Easiest API:
lvconvert --chunksize XX --thinpool data_lv metadata_lv
More functionality extensions will follow up.
TODO: Code needs some rework since a lot of same code is getting copied.
When mirrors are up-converted, a transient mirror layer is put in so that
only the new devices are sync'ed. That transient layer must carry the tags
of the original mirror LV, otherwise it will fail to activate when activation
is regulated by lvm.conf:activation/volume_list. The conversion would then
fail.
The fix is to do exactly the same thing that is being done for linear ->
mirror converting (lib/metadata/mirror.c:_init_mirror_log()). We copy the
tags temporarily for the new LV and remove them after the activation.
Snapshots of RAID logical volumes are allowed (including "raid1"). However,
snapshots of "mirror" logical volumes has been disallowed due to unsolvable
issues inherent to the design. The fact that mirroring (dm-raid1.c) must
stop all I/O as the result of a failure and wait for userspace intervention
can lead to a circular dependency if userspace is simultaneously waiting for
snapshots (on mirrors) to make an I/O update before proceeding.
Various snapshot on mirror tests have been removed as a result.
Looking at the code in cmirrord/local.c, we can see the various different
request types handled in different ways. Some information that is non-changing
does not need to go around the cluster and can be short-circuited. For
example, once the cluster mirror is in-sync, it is pointless to continue
sending that query around the cluster. We can save network bandwidth and reply
directly back to the kernel. When it comes to status information, there are
two types 'TABLE' and 'INFO'. The 'TABLE' information never changes and
belongs to the group of requests that can be safely short-circuited. The
'STATUS' information can change - and will change if a device fails. Thus it
cannot be short-circuited, but this is exactly what was found. The 'STATUS'
information request was being short-circuited and therefore never reporting the
failure condition to anyone other than the "server" that experienced it
directly.
If two devices in an array failed, it was previously impossible to replace
just one of them. This patch allows for the replacement of some, but perhaps
not all, failed devices.
Thanks to agk for providing the patch that prevents resume from attempting
(and then failing) to create error devices which already exist; having been
created by a corresponding suspend operation.
In some occasional case dmevent restart was experiencing problems
with obtaining pid lockfile. So this patch tries to send several more kill
message until daemon kills itself so there is would reponse.
With this small loop the restart seems to work reliable,
although the loopsize and usleep are just randomly picked for now.
Just to make it clearer since there is the "dmsetup info -c -o blkdevname"
as well that shows the "block device name for this mapping", having a
"BlkDevName" header on output.
It's a bit confusing then if the "dmsetup info -c -o devs_used,blkdevs_used"
is named with a plural "DevNames"/"BlkDevNames" but at the same time having
a totally different meaning than the singular form "BlkDevName".
DevNames --> DevNamesUsed
BlkDevNames --> BlkDevNamesUsed
...makes it much more comprehensible.
The 'mirror' segtype and 'raid1' segtype both set the 'MIRRORED' flag.
However, due to differences in the way these device-mapper targets behave
'mirror' must be suspended with the 'noflush' option and 'raid1' does not
have to be.
This patch ensures that when the 'MIRRORED' flag is checked to see if
'noflush' is needed that it does not also set it for 'raid1' by mistake.
