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all but one mirror leg.
<patch header>
To handle a double failure of a mirrored log, Jon's two patches are
commited, however, lvconvert command can't still handle an error
when mirror leg and mirrored log got failure at the same time.
[Patch]: Handle both devices of a mirrored log failing (bug 607347)
posted: https://www.redhat.com/archives/lvm-devel/2010-July/msg00009.html
commit: https://www.redhat.com/archives/lvm-devel/2010-July/msg00027.html
[Patch]: Handle both devices of a mirrored log failing (bug 607347) -
additional fix
posted: https://www.redhat.com/archives/lvm-devel/2010-July/msg00093.html
commit: https://www.redhat.com/archives/lvm-devel/2010-July/msg00101.html
In the second patch, the target type of mirrored log is replaced with
error target when remove_log is set to 1, but this procedure should be
also used in other cases such as the number of mirror leg is 1. This
patch relocates the procedure to the main path.
In addition, I added following three changes.
- Removed tmp_orphan_lvs handling procedure
It seems that _delete_lv() can handle detached_log_lv properly
without adding mirror legs in mirrored log to tmp_orphan_lvs.
Therefore, I removed the procedure.
- Removed vg_write()/vg_commit()
Metadata is saved by vg_write()/vg_commit() just after detached_log_lv
is handled. Therefore, I removed vg_write()/vg_commit().
- With Jon's second patch, we think that we don't have to call
remove_mirror_log() in _lv_update_mirrored_log() because will be
handled remove_mirror_images() in _lvconvert_mirrors_repaire().
</patch header>
Signed-off-by: Takahiro Yasui <takahiro.yasui@hds.com>
Reviewed-by: Petr Rockai <prockai@redhat.com>
Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
The cluster log daemon (cmirrord) is not multi-threaded and
can handle only one request at a time. When a log is stacked
on top of a mirror (which itself contains a 'core' log), it
creates a situation that cannot be solved without threading.
When the top level mirror issues a "resume", the log daemon
attempts to read from the log device to retrieve the log
state. However, the log is a mirror which, before issuing
the read, attempts to determine the 'sync' status of the
region of the mirror which is to be read. This sync status
request cannot be completed by the daemon because it is
blocked on a read I/O to the very mirror requesting the
sync status.
With mirror_log_fault_policy of 'remove' and mirror_image_fault_policy
of 'allocate', the log type of the mirror volume is converted from
'disk' or 'mirrored' to 'core' when all mirror legs but one in a mirror
volume broke.
Keep new_log_count as a number of valid log devices by using log_count
variable for a temporary usage in the first phase of error recovery
in _lvconvert_mirrors_repair().
Signed-off-by: Takahiro Yasui <takahiro.yasui@hds.com>
Reviewed-by: Petr Rockai <prockai@redhat.com>
When splitting off mirror images from a mirror, we always take
LVs from the end of a list. For example, if the mirror sub-devices
are lv_mimage_[012], we should select lv_mimage_2 if splitting off
one image. However, lv_mimage_0 was being selected instead.
The problem came from calling '_move_removable_mimages_to_end'
when it was unnecessary to do so. When the user /does/ specify
specific devices to be removed, this function properly moved the
appropriate LVs to the end of the list for extraction. However,
if the user /doesn't/ give any specific PVs, the function should
do nothing. '_move_removable_mimages_to_end' was keying off of
whether 'removable_pvs' was NULL or not and this value was
improperly being populated with the set of all available PVs.
This was causing '_move_removable_mimages_to_end' to completely
reverse the list, which in turn caused us to extract the
hithertofore front-of-the-list LVs.
An unhandled condition allowed the command to terminate
cleanly without a warning. Added a check for the
'--splitmirrors' argument to allow execution to the lower
level function that has the check to see if the user is
trying to split a linear device. You should now see a
message if you try to use --splitmirrors on a linear device.
Pass metadataignore through PV creation / setup paths.
As a result of this cleanup, we can remove the unnecessary setting
of mda_ignore bits inside pvcreate_single(), after call to pv_create.
For now, just set metadataignore to '0' in some places. This is
equivalent to the prior functionality, although the 0 is given
by the caller not hardcoded in _mda_setup() call.
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
When using vgmetadatacopies value other than "umanaged" (0), prompt
the user if the usage of --metadataignore would change the value of
vgmetadatacopies. The main 2 cases are:
1) pvchange --metadataignore
2) vgextend --metadataignore
We leave the prompt check in the tools, and do not change anything
if the user says 'n'.
Examples:
vgextend --metadataignore y vgtest /dev/loop0
Setting metadataignore will override preferred number of copies of VG vgtest metadata.
Are you sure? [y/n]: y
No physical volume label read from /dev/loop0
Physical volume "/dev/loop0" successfully created
Volume group "vgtest" successfully extended
pvchange --metadataignore y /dev/loop3
Setting metadataignore on /dev/loop3 will override preferred number of copies of VG vgtest metadata.
Are you sure? [y/n]: y
WARNING: Changing preferred number of copies of VG vgtest metadata from 3 to 2
Physical volume "/dev/loop3" changed
1 physical volume changed / 0 physical volumes not changed
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Rather than attempting to remove all the images of a mirrored
log volume via remove_mirror_images, simply remove the log
if all its devices have failed.
Taka was the first to report that there is still an outstanding
issue with handling this case. I've managed to reproduce it
only very rarely, and am still working on identifying the problem.
Failing to handle the problem rarely is better than not handling
the scenario at all, so I'm checking this in.
Allow metadataignore flag to be passed in to pvcreate.
Ideally, more refactoring of the mda allocation / initialization
is warranted, but for now, we just add another parameter to 'add_mda'
to take an existing mda ignored flag. We need to do this or pv_write
loses the state of the mda 'ignored' flag before copying and writing
to disk.
In preparation to call this from both pvcreate as well as pvchange,
move the guts of metadataignore into a library function.
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Allowing an 'all' and 'unmanaged' value is more intuitive, and
provides a simple way for users to get back to original LVM behavior
of metadata written to all PVs in the volume group.
If the user requests "--vgmetadatacopies unmanaged", this instructs
LVM not to manage the ignore bits to achieve a specific number of
metadata copies in the volume group. The user is free to use
"pvchange --metadataignore" to control the mdas on a per-PV basis.
If the user requests "--vgmetadatacopies all", this instructs LVM
to do 2 things: 1) clear all ignore bits, and 2) set the "unmanaged"
policy going forward.
Internally, we use the special MAX_UINT32 value to indicate 'all'.
This 'just' works since it's the largest value possible for the
field and so all 'ignore' bits on all mdas in the VG will get
cleared inside _vg_metadata_balance(). However, after we've
called the _vg_metadata_balance function, we check for the special
'all' value, and if set, we write the "unmanaged" value into the
metadata. As such, the 'all' value is never written to disk.
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Now that we have both --pvmetadatacopies and --vgmetadatacopies,
we need to make sure --metadatacopies gets interpreted correctly.
For pv commands, --metadatacopies should imply --pvmetadatacopies,
and for vg commands, --vgmetadatacopies.
Note: this will change the behavior of vgcreate with --metadatacopies
to be a synonym for --vgmetadatacopies. Previously, --metadatacopies
would apply to any PVs given with vgcreate that needed an implicit
pvcreate. As a result, one small change is needed to one of the nightly
tests - t-vgcreate-usage.
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
When vgmerge is called we move the mdas from the source to the
destination. With metadata balancing we now have another mda
list, fid->metadata_areas_ignored, so move the mdas on this list
as well.
This patch should not matter as the code is written today. However
we include it for completeness in the case that _vgmerge_single()
is refactored and/or moved into a library function.
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Allow parsing of --vgmetadatacopies for vgcreate. Accept
--metadatacopies as a synonym for --vgmetadatacopies.
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
When a user explicitly sets a new mda ignore value for a PV, we
should update vg_mda_copies accordingly. When the VG is written
out, the user would not want the new ignore state to get lost as
a result of the vg_mda_copies value and logic in the vg_write
path.
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Update logic in vgchange to handle --vgmetadatacopies, allow
--metadatacopies as a synonym to --vgmetadatacopies,
and add these parameters to args.h and commands.h
Forbit both --vgmetadatacopies and --metadatacopies as only
one allowed.
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Add a field to struct volume_group to later implement metadata
balancing:
- mda_copies: target # of non-ignored mdas in the VG; default 0 (do
not control pv 'ignore mdas' bit.
This patch just adds the parameter to the structures with the default
values but does not modify any commands. Should be no functional change.
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
This patch just modifies pvchange to call the underlying ignore
functions for mdas. Ensure special cases do not reflect changes
in metadata (PVs with 0 mdas, setting ignored when already ignored,
clearing ignored when not ignored).
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
the failure of a device that contained both a image of
a mirror and an image of the mirrored log. The order
of the handling of those faults was important (and
wrong), this patch corrects that.
Patch-From: Takahiro Yasui <tyasui@redhat.com>
Activate only the first replicator-dev LV, that activates all other
related LVs from Replicator. In case of error during this activation,
it will not retry again for other heads (less confusing error log).
As for _process_one_vg() we need similar retry loop for
process_each_lv_in_vg(). This patch retries to process
failed LVs with reopened VGs.
Patch does not add any extra repeated invocations if there is not
found any missing VG during LV processing.
Patch modifes behavior of _process_one_vg().
In the first pass vg_read() collectis for replicator sorted list of
additional VGs during lock_vol().
If any other VG is needed by the replicator and it is not yet opened
then next iteration loop is taken with all collected VGs.
Flag vg->cmd_missing_vgs detects missing VGs.
Patch adds failed_lvnames to the list of parameters for process_each_lv_in_vg().
If the list is not NULL it will be filled with LV names of failing LVs
during function execution.
Application could later reiterate only on failed LVs.
Earlier patches added some infrastructure to lookup a vgname from
a pvname. We now can cleanup some of the pvchange and other code
by requiring callers that want to modify some pv property:
1) lookup the vgname by the pvname
2) use the vgname to obtain a vg handle
3) get the pv handle from the vg handle
This should work going forward and be a much cleaner interface,
as we move away from pvs as standalone objects.
A shortcut for --ignorelockingfailure, --ignoremonitoring, --poll n options
and LVM_SUPPRESS_LOCKING_FAILURE_MESSAGES environment variable used all at
once in initialisation scripts (e.g. rc.sysinit or initrd).
We can use it even in read-only environment where a try to initialise
file-based locking fails (not to mention other processing related with
lvm2 init). Simply, we want to output the version only, nothing else.
And this should always work.
This rule appeared in udev v152 and it helps us to support spurious events
where we didn't have any flags set (events originated in udevadm trigger
or the watch rule). These flags are important to direct the rule application.
Now, with the help of this rule, we can regenerate old udev db content.
To implement this correctly, we need to flag all proper DM udev events with
DM_UDEV_PRIMARY_SOURCE_FLAG. That happens automatically for all ioctls
generating events originated in libdevmapper.
Allow lv_remove_with_dependencies() to know the top-level LV that was
requested to be removed (otherwise it recurses and we lose context).
A merging snapshot cannot be removed directly but the associated origin
can be. Disallow removal of a merging snapshot unless the associated
origin is also being removed.
(process_each_lv_in_vg) provides it.
Also, removing this check from _lvs_single now allows displaying hidden
LVs that are specifically named on the command line.
There's no need for foreign udev rules to touch LVM reserved devices
(snapshot, pvmove, _mlog, _mimage, _vorigin) even if they happen to
be visible. The same applies for /dev/disk content - no need to create
any content for these devices (and so no need to run any "blkid" etc.).
This also prevents setting any inotify "watch" from udev rules on such
devices that is a source of race conditions (the rules need to honor
DM_UDEV_DISABLE_OTHER_RULES_FLAG for this to work though).
Now that we have library functions to add/delete a pv from the vg->pvs
list, call them from everywhere.
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Patch is inspired by Debian's extra patch.
- removes OWNER & GROUP make vars they are parts of INSTALL command.
- adds INSTALL_PROGRAM for executable, uses $(INSTALL)
- adds INSTALL_DATA for non-executable data, uses ($INSTALL)
- adds INSTALL_WDATA for writable non-executable data, uses ($INSTALL)
- adds configure option --enable-write_install - to support
installatin of writable files used by distribution
- replaces usage of ifeq @LIB_SUFFIX@ with $(LIB_SUFFIX)
- installs .a files from static builds without executable flag
- installs .a files to $(usrlibdir) instead of $(libdir)
- installs all static binaries to $(staticdir)
- create .so links for devel package in $(usrlibdir) instead of
$(libdir)
- makes .so and .so.LIB_VERSION files within builddir
- removes VERSIONED_SHLIB and created versioned LIB_SHARED automagicaly
- install LIB_SHARED via install_lib_shared target
- install plugins via install_lib_shared_plugin target
- prints whole 'install' command during installation instead of less
informative "Installing $(something) $(somewhere)"
- install multiple man pages with one INSTALL command
- use DISTCLEAN_TARGETS instead of creating multiple distclean targets
Usage of VPATH makes troubles when used within $(builddir).
Not only source files are being found through VPATH,
but targets as well. (make --debug=v)
Thus if user builds the code in $(srcdir) and also in some $(builddir)
he gets mangled results as some generated files (i.e. .export.sym)
are 'reused' from $(srcdir) instead of $(builddir).
This patch switches to use vpath were we could explicitly name
suffixes that should be looked via vpath - we must take care,
we do not generate files with these suffixes:
.c, .in, .po, .exported_symbols
clvmd does not propagate DMEVENTD_MONITOR_IGNORE.
Update get_activation_monitoring_mode() to check if the VG that the
LV is being activated in is clustered. If so, skip it.
Any get_activation_monitoring_mode() error will cause the associated LV
(or VG) to be skipped during activation. Both vgchange_single() and
lvchange_single(), which call get_activation_monitoring_mode(), are
called by their respective process_each_..() method.
in clvmd, dmevend, man, tests.
Don't include dependency files for clow and cscope.out targets
Improve dependency tracking for dmeventd and liblvm2cmd sources.
to obtain sources. Create make.tmpl target for
simplier generation of cflow files with the help of
CFLOW_LIST, CFLOW_LIST_TARGET, CFLOW_TARGET.
Still cflow usage is not perfect.
This check-in enables the 'mirrored' log type. It can be specified
by using the '--mirrorlog' option as follows:
#> lvcreate -m1 --mirrorlog mirrored -L 5G -n lv vg
I've also included a couple updates to the testsuite. These updates
include tests for the new log type, and some fixes to some of the
*lvconvert* tests.
. Add "monitoring" option to "activation" section of lvm.conf
. Have clvmd consult the lvm.conf "activation/monitoring" too.
. Introduce toollib.c:get_activation_monitoring_mode().
. Error out when both --monitor and --ignoremonitoring are provided.
. Add --monitor and --ignoremonitoring support to lvcreate. Update
lvcreate man page accordingly.
. Clarify that '--monitor' controls the start and stop of monitoring in
the {vg,lv}change man pages.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This prevents some confusion when libudev was not found so udev_sync was disabled
automatically. Configure was successful though giving only a tiny warning.
Also, if "dmsetup udevcreatecookie" is used, never return 0x000000 as a result if
udev is not running and keep the output blank.
Prevent lvresize from being able to resize internal LVs: mirror legs
(*_mimage_*), mirror log (*_mlog), snapshot placeholder LVs (snapshot*)
and others. Resizing these would leads to unexpected metadata and
sometimes crashes (in case of growing snapshot*).
When we pv_read() a device that has an orphan vgname, we might need to scan
the system to be sure this is true. However, if the PV has mdas, there's
no way possible for it to have an orphan vgname unless it is a true orphan.
Some areas of the code were optimized to take advantage of this fact, while
others were not (we would still do the expensive scan if a device had mdas
but had an orphan VG).
This patch unifies the code so that every place we are operating on such
a PV, we skip the expensive scan if there are mdas.
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Acked-by: Petr Rockai <prockai@redhat.com>
Acked-by: Alasdair G Kergon <agk@redhat.com>
This patch adds a new implementation of locking function instead
of mlockall() that may lock way too much memory (>100MB).
New function instead uses mlock() system call and selectively locks
memory areas from /proc/self/maps trying to avoid locking areas
unused during lock-ed state.
Patch also adds struct cmd_context to all memlock() calls to have
access to configuration.
For backward compatibility functionality of mlockall()
is preserved with "activation/use_mlockall" flag.
As a simple check, locking and unlocking counts the amount of memory
and compares whether values are matching.
For static builds dependency for SELinux libs is not handled by 'ar'.
Till better solution is found, for static builds STATIC_LIBS is used.
Patch updates SELinux detection to use 3rd & 4th parameter for Success/Fail.
Also removes detection of pthread from this check as we know which
version of libdevmapper we are going to link with lvm after merge.
SELinux header check moved to the SELinux test code.
Create new substituted variable PTHREAD_LIBS and link this library
only with tools/libs which really needs it - i.e. dmeventd.
Check for libpthread only for builds with clvmd or dmeventd.
Remove variable LIB_PTHREAD
Modify linking of readline library. Create new substituted varible
READLINE_LIBS - readline library is linked ONLY with tools that really use
it - i.e. lvm. (Static lvm does not use readlin).
Previous behaviour put this library into the variable LIBS and thus
linked it with all created object files of lvm project (i.e. plugins...).
READLINE detection is simplified.
Termcap library is linked in only if readline library doesn't have its own
dependency (i.e. old distributions).
Similar refactoring to vgchange - pull out common parts and put into
library function for reuse. Should be no functional change.
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Pull out common code to be called from tools as well as lvm2app.
Leave archive() at tool level so we can use from vgcreate
as well as vgchange. Should be no functional change.
- add stack macro in vgchange
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Add a merging snapshot to the deptree, using the "error" target, rather
than avoid adding it entirely. This allows proper cleanup of the -cow
device without having to rename the -cow to use the origin's name as a
prefix.
Move the preloading of the origin LV, after a merge, from
lv_remove_single() to vg_remove_snapshot(). Having vg_remove_snapshot()
preload the origin allows the -cow device to be released so that it can
be removed via deactivate_lv(). lv_remove_single()'s deactivate_lv()
reliably removes the -cow device because the associated snapshot LV,
that is to be removed when a snapshot-merge completes, is always added
to the deptree (and kernel -- via "error" target).
Now when the snapshot LV is removed both the -cow and -real devices
get removed using uuid rather than device name. This paves the way
for us to switch over to info-by-uuid queries.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
- add DM_UDEV_DISABLE_LIBRARY_FALLBACK udev flag to rely on udev only
- export dm_udev_create_cookie function to create new cookies on demand
- add --udevcookie, udevcreatecookie and udevreleasecookie for dmsetup
(to support "udev transactions" where one cookie value can be used for
several dmsetup calls)
- don't use DM_UDEV_DISABLE_CHECKING env. var. anymore and set the state
automatically (based on udev and libdevmapper dev path comparison)
This change was deferred to help ease the review of previous refactoring
related to using process_each_lv() for lvconvert's merge support. Not
that doing so _really_ helped but...
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Switch lvconvert's --merge code over to using process_each_lv(). Doing
so adds support for a single 'lvconvert --merge' to start merging
multiple LVs (which includes @tag expansion).
Add 'lvconvert --merge @tag' testing to test/t-snapshot-merge.sh
Adjust man/lvconvert.8.in to reflect these expanded capabilities.
The lvconvert.c implementation requires rereading the VG each iteration
of process_each_lv(). Otherwise a stale VG instance associated with
the LV passed to lvconvert_single_merge() would result in stale VG
metadata being written back out to disk. This overwrote new metadata
that was written when a previous snapshot LV finished merging (via
lvconvert_poll). This is only an issue when merging multiple LVs that
share the same VG (a single VG is typical for most LVM configurations on
system disks).
In the end this new support is very useful for performing a "system
rollback" that requires multiple snapshot LVs be merged to their
respective origin LV.
The yum-utils 'fs-snapshot' plugin tags all snapshot LVs that it creates
with a common 'snapshot_tag' that is unique to the yum transaction.
Rolling back a yum transaction, that created LVM snapshots with the tag
'yum_20100129133223', is as simple as:
lvconvert --merge @yum_20100129133223
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
refactoring.
Document the need to cleanup the "name" args passed around polldaemon,
lvconvert and pvmove. It is quite a mess.
Annotate the unused nature of the existing poll_fns->get_copy_vg
methods' 'uuid' arg.
depending on if the mirror has a 'core' or 'disk' log. When there
is a disk log, the new leg is added by stacking a new mirror on
top of the old (one leg is the old mirror and the other leg is the newly
added device). When the log is a 'core' log, the new leg is simply added
to the existing mirror and all the devices are re-synced.
The logic that handles collapsing the stacked 'disk' log mirror was
having the effect of causing 'core' logged mirrors to begin resync'ing
for a second time. I have used the 'CONVERTING' flag to indicate that
a mirror is converting by way of stacking. This is no longer set for
up-converting core logs. The final 'collapse' logic can safely be skipped
for 'core' log mirrors - getting rid of the second resync.
Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
where we should not expose internal VG names/uuids (the ones with "#" prefix )through the
interface. Otherwise, we could end up with library users opening internal VGs which will
initiate locking mechanism that won't be cleaned up properly.
"#orphans_{lvm1, lvm2, pool}" names are treated in a special way, they are truncated first
to "orphans" and this is used as a part of the lock name then (e.g. while calling lvm_vg_open()).
When library user calls lvm_vg_close(), the original name "orphans_{lvm1, lvm2, pool}"
is used directly and therefore no unlock occurs.
We should exclude internal VG names and uuids in the lists provided by lvmcache:
lvmcache_get_vgids() and lvmcache_get_vgnames().
Allow the number of logical extents to be expressed (for a snapshot) as
a percentage of the total space in the Origin Logical Volume with the
suffix %ORIGIN.
Update the relevant man pages accordingly. Eliminate inconsistencies
between the man pages and tools/commands.h
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
When activation of pvmove mirror fails on cluster, some nodes
still possibly succeeded in activation.
- Explicitly deactivate that mirror to be sure
- properly pair suspend/resume calls to not cause memory lock problems in clvmd
Code cannot simply call _finish_pvmove on cluster in this situation, because
changed LVs are suspended twice (causing memory inbalance) and also temporary
mirror is activated when it is not expected (and we know that it failed already).
Patch prepares special function which remove temporary mirror references from
metadata and then resumes changed LVs.
Support "wait before testing" using '+' in pvmove and lvconvert
interval. Doing so overrides the new default of sleeping after checking
the LV's progress.
Sleeping before checking progress can lead to extraneous polldaemons
being left running. These polldaemons would have otherwise exited had
they checked before sleeping. Checking progress before sleeping helps
workaround the subtly unreliable nature of "finished" state checking
in _percent_run.
Update test/t-mirror-names.sh to use '+' when providing its lvconvert
interval.
more descriptive message if locking fails instead of
"Locking type -1 initialisation failed."
Use read-only locking instead of misleading ignorelocking option
in message.
DSO is currently not dl_close-ing pluing during it is unregister handling,
so clear structure and related counter, so there are no memory problems.
Futher fixes are needed.
'const'. Be consistent with its use (and dev_manager_snapshot_percent()).
Pass 'lv' from dev_manager_snapshot_percent() to _percent() to
_percent_run(). _percent_run() always dereferenced 'lv' (when
initializing segh) even though it may have been NULL (as was the case
until now for dev_manager_snapshot_percent()).
If a "snapshot-origin" LV (snapshot-merge whose merge was deferred
becuase it was open) was passed to _percent_run() it would always return
100%.
Update _percent_run() to NOT return PERCENT_100 et. al. if
->target_percent() wasn't ever called and supplied 'lv' is a merging
origin. A default return of 100% does not work for snapshot-merge.
Also tweak a related lvconvert log_error() to include "Aborting merge."
Eliminate 'merging_snapshot' from 'struct logical_volume' and just use
'snapshot' for origin lv's reference to the merging snapshot; also set
MERGING in the origin lv's status.
If either the origin or snapshot that is to be merged is open the merge
will not start; only the merge metadata will be written. The merge will
start on the next activation of the origin (or via lvchange --refresh)
IFF both the origin and snapshot are closed.
Merge on activate is particularly important if we want to merge over a
mounted filesystem that cannot be unmounted (until next boot) --- for
example root.
