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Add more code to properly store status for snapshot segment
maintaining lvm2 fiction of COW and snapshot internal volumes.
The key issue here is however not though-through reporting
logic - as there is no single answer for whole line state.
It not counting with layer and we may need few more ioctl to
cover all reporting needs depending upon what is actually
needed.
In reality we need to 'cache' more ioctl status queries for
individual LVs and their segments (so they checked at most once).
The other 'hard' topic for conversion is mirror segment handling.
Also we definitelly need to relocate some logic into segment's methods,
yet it might be complex as we have not clear border between targets.
TODO: define more clearly how are reporting fields defined in case
we 'stack' volumes like - cache of stacked thin LV snapshot origin.
To get better control when flushing is used add extra arg when
setting up dm task.
By default now check dm device status without flush.
(At this moment this should effect only thin and cache volumes).
Also switch dev_manager_thin_pool_status() to use more
readable 'flush' parameter instead of 'no_flush'.
Before executing modprobe for given module name, just check
if the module is not already present in /sys/module.
Useful when checking dm-cache-policy modules as we do not
having matching interface like for targets.
A snapshot merge into its origin cannot be initiated while the devices
are in use. If there is outside interference (such as from udev),
the suspend (preload) and resume stages can reach conflicting decisions
about whether or not to proceed.
Try to make the logic more robust by checking the inactive or live
table during resume. (This is still not perfect.)
Commit 844b009584 tried to move
limit for usage of noflush to 'preload' however this was not
correctly processed.
Intead explicitly check for which types we do not want noflush
and also add debug message in this case.
dmeventd daemon may call further code itself that looks at /dev, e.g.
via dmeventd_lvm2_command call. We need to have a consistent view of
the /dev content at that time. Therefore, sync /dev content before
calling monitoring hook which contacts dmeventd.
This problem was quite hidden before, but now it has manifested itself
because of recent additions to dev-cache code where we started looking
at device holders as seen in sysfs. What happened here was that the
device was already in sysfs, but not yet under /dev and this triggered
the new error message sometimes:
log_error("%s: failed to find associated device structure for holder %s.", devname, devpath);
This problem has manifested recently in our api/pytest.sh test from
testsuite where we create thin pool LVs and thin LVs and hence it also
causes dmeventd to be used as well and these error messages were
visible there.
Remove long outstand unused code lines, which were already
been obsoleted by other code.
Statuses and snapshot tree creation is already handled differently.
Also drop some 'extra' log_error() and use only stack;
since error has already been reported.
lv preload for detached LVs started to be used also
for various other types which just happens to pass through
weak if() condition.
TODO: find here better solution to rather explicitly check
for types we really need to preload.
We do not won't to 'expose' internals of VG struct.
ATM we use lists to keep all LVs - we may want to switch
to better struct for quicker 'search'.
Since we do not need 'lists' but always actual LV,
switch find_lv_in_vg_by_lvid() to return LV,
and replaces some use case of find_lv_in_vg()
with 'better' working find_lv() which already
returns LV.
Existing messaging intarface for thin-pool has a few 'weak' points:
* Message were posted with each 'resume' operation, thus not allowing
activation of thin-pool with the existing state.
* Acceleration skipped suspend step has not worked in cluster,
since clvmd resumes only nodes which are suspended (have proper lock
state).
* Resume may fail and code is not really designed to 'fail' in this
phase (generic rule here is resume DOES NOT fail unless something serious
is wrong and lvm2 tool usually doesn't handle recovery path in this case.)
* Full thin-pool suspend happened, when taken a thin-volume snapshot.
With this patch the new method relocates message passing into suspend
state.
This has a few drawbacks with current API, but overal it performs
better and gives are more posibilities to deal with errors.
Patch introduces a new logic for 'origin-only' suspend of thin-pool and
this also relates to thin-volume when taking snapshot.
When suspend_origin_only operation is invoked on a pool with
queued messages then only those messages are posted to thin-pool and
actual suspend of thin pool and data and metadata volume is skipped.
This makes taking a snapshot of thin-volume lighter operation and
avoids blocking of other unrelated active thin volumes.
Also fail now happens in 'suspend' state where the 'Fail' is more expected
and it is better handled through error paths.
Activation of thin-pool is now not sending any message and leaves upto a tool
to decided later how to finish unfinished double-commit transaction.
Problem which needs some API improvements relates to the lvm2 tree
construction. For the suspend tree we do not add target table line
into the tree, but only a device is inserted into a tree.
Current mechanism to attach messages for thin-pool requires the libdm
to know about thin-pool target, so lvm2 currently takes assumption, node
is really a thin-pool and fills in the table line for this node (which
should be ensured by the PRELOAD phase, but it's a misuse of internal API)
we would possibly need to be able to attach message to 'any' node.
Other thing to notice - current messaging interface in thin-pool
target requires to suspend thin volume origin first and then send
a create message, but this could not have any 'nice' solution on lvm2
side and IMHO we should introduce something like 'create_after_resume'
message.
Patch also changes the moment, where lvm2 transaction id is increased.
Now it happens only after successful finish of kernel transaction id
change. This change was needed to handle properly activation of pool,
which is in the middle of unfinished transaction, and also this corrects
usage of thin-pool by external apps like Docker.
Older lvm2 tools where always providing linear mapping for thin pool.
Recent lvm2 version however support external usage of thin pool and
empty/unused pools are loaded without such external linear mapping.
So this patch covers 'upgrade' problem, where older tool has activated
thin-pool with 'linear' layer mapping, and newer tools didn't expected
such mapping to exist and were not able to deactivate such table.
So before checking for new layout in dm-table, check if there is not
an old one already there.
Check splitted leg is active before preload.
(Since splitmirrors currently only does work active raid volumes
it's not a change for current code flow).
Minor optimization included - when already positively checked
for raid image don't check again for raid metadata.
for_each_sub_lv() normally does not put pool_lv into deps.
So for now go around it in 'lv_preload()' and add explicit
call with pool.
TODO: think about a better way, we want pool_lv deps only in certain
moments, so maybe for_each_sub_lv() needs new arg for this.
When raid is being splitted, extracted leg & metadata
is still floating in the table - and thus we need to
detect this case and properly preload their matching
table so consequent activation of extracted LVs properly
renames (and FREES) existing raid images, so ongoing
image name shifting will work.
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.
When creating/activating clustered mirrors, we should have cmirrord
available and running. If it's not, we ended up with rather cryptic
errors like:
$ lvcreate -l1 -m1 --type mirror vg
Error locking on node 1: device-mapper: reload ioctl on failed: Invalid argument
Failed to activate new LV.
$ vgchange -ay vg
Error locking on node node 1: device-mapper: reload ioctl on failed: Invalid argument
This patch adds check for cmirror availability and it errors out
properly, also giving a more precise error messge so users are able
to identify the source of the problem easily:
$ lvcreate -l1 -m1 --type mirror vg
Shared cluster mirrors are not available.
$ vgchange -ay vg
Error locking on node 1: Shared cluster mirrors are not available.
Exclusively activated cluster mirror LVs are OK even without cmirrord:
$ vgchange -aey vg
1 logical volume(s) in volume group "vg" now active
Just call return 0 directly on error path, without using
"goto" - the code is short, no need to use it this way
(the dead code appeared as part of further changes in this
function).
- Add separate lv_status fn (if we're interested only in seg status,
but not lv info at the same time as it is with existing
lv_info_with_seg_status fn). So we 3 fns:
- lv_info (existing one, runs only info ioctl, fills in struct lvinfo only)
- lv_status (new one, runs status ioctl, fills in struct lv_seg_status only)
- lv_info_with_seg_status (existing one, runs status ioctl, fills
in struct lvinfo as well as lv_seg_status)
- Add more comments in the code explaining the difference between lv_info,
lv_status and lv_info_with_seg_status and their return values.
- Move decision whether lv_info_with_seg_status needs to call only
status ioctl (in case the segment for which we require status is from
the LV for which we require info) or separate status and info ioctl
(in case the segment for which we require status is from different
LV that the one for which we require info) into
lv_info_with_seg_status fn so caller doesn't need to bother about
this at all.
- Cleanup internal interface for this seg status so it's more readable.
