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When a mirror is being downconverted in a cluster, a series of suspends and
resumes is executed.
With the change to using UUIDs in dev_manager instead of names, the behaviour
has changed with regards to including an _mlog in the deptree of a logical
volume. In the old (pre-UUID-enabled) code, the _mlog would appear in a deptree
of any volume purely based on a name match: a linear volume foo would include
foo_mlog in its dependencies if that happened to exist. This behaviour was
fixed and the mlog is now only included for mirrors.
By a coincidence, this mlog bug had been hiding a different bug in clvmd. When
a mirror is being dismantled (and converted to a linear volume), it is first
suspended as a whole, then later resumed in parts. Nevertheless, the overall
memlock balance is maintained in this operation. The problem kicks in, because
even though the mirror log was suspended as part of the mirror, when the
dismantled mirror is resumed again, it is no longer a mirror and therefore the
mirror log stays suspended. This would not be a problem in itself, since
_delete_lv (from metadata/mirror.c) is called on it subsequently, which does an
activate/deactivate cycle and removes the LV. The activate/deactivate cycle
correctly prompts clvmd to resume the device: however, in doing this, it will
issue an unpaired resume operation (the suspend that caused the mirror log to
be suspended is paired with resuming the dismantled mirror later). We have
concluded that the path in clvmd should never affect memlock_count, since there
should never be an unmatched explicit suspend preceding this resume.
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.
Print device name when setting or clearing metadata ignore bit.
Example:
label/label.c:160 /dev/loop2: lvm2 label detected
cache/lvmcache.c:1136 lvmcache: /dev/loop2: now in VG #orphans_lvm2 (#orphans_lvm2)
metadata/metadata.c:4142 Setting mda ignored flag for metadata_locn /dev/loop2.
format_text/text_label.c:318 Skipping mda with ignored flag on device /dev/loop2 at offset 4096
Logging isn't ideal, especially for mda_set_ignore. Ideally we'd
like to display the device name and offset in this case but this
requires a bit more work and a per-format 'mda_description' function
pointer definition (we don't have access to mda_context in
metadata.c).
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>
There's an intermittent failure with vgcfgbackup that seems to have been
introduced with the metadataignore / vgmetadatacopies patchset.
Intermittent failures are often the result of uninitialized data,
so this patch calls zalloc in a few places it might matter.
Update example.conf to describe vgmetadatacopies. Provide an
explanation for the '0' ("unmanaged") value.
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>
The check in vg_split_mdas will trigger an error if the 'from' vg
list is empty. However, this might be ok in some instances now
that we have ignored mdas. Relax this check so an error is triggered
only in the case where there's truly no more mdas in the 'from'
vg.
One example of where this makes a difference is with vgreduce.
If we try to vgreduce a PV with un-ignored mdas, this should trigger
the balancing function to un-ignore mdas on another PV in the VG.
However, we don't get to vg_write() before we fail because this
list size check fails, and we see an error message indicating:
"Cannot remove final metadata area ..."
Another example is with vgsplit into a new VG, where the PVs
being moved contain all ignored mdas. We must move the mdas on
fid->metadata_areas_ignored from 'vg_from' to 'vg_to'.
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
The vgextend path calls add_pv_to_vg(). Inside add_pv_to_vg(),
we must ensure we pass the correct mdas list into pv_setup(), as
copies of mdas are placed on the vg->fid list. If we don't place
the mdas on the correct vg->fid list, the various counts may be
incorrect and the metadata balance algorithm will not work when
called from vg_write() path.
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>
Compare the value of the newly added vg_mda_copies field
(--vgmetadatacopies parameter) with the current count of
in-use mdas and ignoring or unignoring mdas as necessary to
get to the target count. Also, as a safety check before
returning, ensure we have at least one mda enabled.
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>
This patch adds the ability to read/write the vg->mda_copies values
from/to the vg metadata.
If we read the VG metadata and this field does not exist, we set
mda_copies to the default value of 0. Later in the code, we use
this special '0' value to indicate a disable of metadata balancing.
This should preserve existing LVM behavior and ensure metadata balancing
can be turned off should the need arise.
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
This patch adds the get and partially implemented set function.
The 'set' function should probably ignore or un-ignore metadata areas
based on new values.
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 adds a vgmetadatacopies parameter for metadata balancing.
This parameter provides a simple way for users to create a policy for
placing metadata on PVs automatically by LVM. The behavior is implemented
inside LVM by managing the 'ignore' mda bits. We chose the name
'vgmetadatacopies' as this is a natural extension to the existing parameter
'pvmetadatacopies' / 'metadatacopies' in pvcreate.
This is a first step at VG parameter based metadata balancing. Most users
will probably want to state that they want a certain number of PVs to contain
metadata, and they may be less concerned about a specific number of metadata
copies in the volume group. However, for default values (pvmetadatacopies
is 1 by default), the number of metadatacopies in the volume group, and the
number of PVs with metadata are the same. In the future we could add
vgmetadatacopiespvs to define more specifically the number of pvs in the
VG that contain metadata, but for now we start with this parameter.
Another possible future extension would be to define a specific pv tag
to mark the set of PVs that should be used for metadata balancing. This
tag based approach could be used in conjunction with 'vgmetadatacopies'.
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
