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When kernel target reports sync status as 0% it might as well mean
it's 100% in sync, just the target is in some race inconsistent
state - so reread once again and take a more optimistic value ;)
Patch tries to work around:
https://bugzilla.redhat.com/show_bug.cgi?id=1210637
When raid leg is extracted, now the preload code handles this state
correctly and put proper new table entry into dm tree,
so the activation of extracted leg and removed metadata works
after commit.
The previous patch felt short WRT disabling allocation on PVs holding other
legs of the RAID LV persistently; this patch introduces an internal,
transient PV flag PV_ALLOCATION_PROHIBITED to address this very problem.
General problem description for completeness:
An 'lvconvert --repair $RAID_LV" to replace a failed leg of a multi-segment
RAID10/4/5/6 logical volume can lead to allocation of (parts of) the replacement
image component pair on the physical volume of another image component
(e.g. image 0 allocated on the same PV as image 1 silently impeding resilience).
Patch fixes this severe resilince issue by prohibiting allocation on PVs
already holding other legs of the RAID set. It allows to allocate free space
on any operational PV already holding parts of the image component pair.
An 'lvconvert --repair $RAID_LV" to replace a failed leg of a multi-segment
RAID10/4/5/6 logical volume can lead to allocation of (parts of) the replacement
image component pair on the physical volume of another image component
(e.g. image 0 allocated on the same PV as image 1 silently impeding resilience).
Patch fixes this severe resilince issue by prohibiting allocation on PVs
already holding other legs of the RAID set. It allows to allocate free space
on any operational PV already holding parts of the image component pair.
$ lvcreate -l1 -m1 --type mirror vg
Logical volume "lvol0" created.
$ lvconvert --type raid1 vg/lvol0
Before:
$ lvs -a vg
LV VG Active Attr LSize Cpy%Sync Layout Role
lvol0 vg active rwi-a-r--- 4.00m 100.00 raid,raid1 public
[lvol0_mimage_0_rimage_0] vg active iwi-aor--- 4.00m linear private,raid,image
[lvol0_mimage_1_rimage_1] vg active iwi-aor--- 4.00m linear private,raid,image
[lvol0_rmeta_0] vg active ewi-aor--- 4.00m linear private,raid,metadata
[lvol0_rmeta_1] vg active ewi-aor--- 4.00m linear private,raid,metadata
Incorrect name: lvol0_mimage_0_rimage_0
With this patch applied:
$ lvs -a vg
LV VG Active Attr LSize Cpy%Sync Layout Role
lvol0 vg active rwi-a-r--- 4.00m 100.00 raid,raid1 public
[lvol0_rimage_0] vg active iwi-aor--- 4.00m linear private,raid,image
[lvol0_rimage_1] vg active iwi-aor--- 4.00m linear private,raid,image
[lvol0_rmeta_0] vg active ewi-aor--- 4.00m linear private,raid,metadata
[lvol0_rmeta_1] vg active ewi-aor--- 4.00m linear private,raid,metadata
Proper name: lvol0_rimage_0
When we split leg from raid - we take a proper new lock for a new LV.
However for now activation checks only 'existince' of device UUID,
but it's not validating device has a proper name.
As a quick fix call suspend()/resume() to rename after split mirror.
Ask for lock the proper LV.
Use the top-most LV to query for locally exclusive lock.
The rest of operations are then using 'lv_info()'
TODO:
Check all devices are reloaded from proper level.
In general any query on lv_is_active is supposed to be running
ona lv_lock_holder() volume.
Instead of segtype->ops->name() introduce lvseg_name().
This also allows us to leave name() function 'empty' for default
return of segtype->name.
TODO: add functions for rest of ops->
We are not using already defined segement type names where we could.
There is a lot of other places in device-mapper and LVM2 we have those
hardcoded so we should better finally have a common interface in
libdevmapper to avoid this.
Try to enforce consistent macro usage along these lines:
lv_is_mirror - mirror that uses the original dm-raid1 implementation
(segment type "mirror")
lv_is_mirror_type - also includes internal mirror image and log LVs
lv_is_raid - raid volume that uses the new dm-raid implementation
(segment type "raid")
lv_is_raid_type - also includes internal raid image / log / metadata LVs
lv_is_mirrored - LV is mirrored using either kernel implementation
(excludes non-mirror modes like raid5 etc.)
lv_is_pvmove - internal pvmove volume
Use lv_update_and_reload() and lv_update_and_reload_origin()
to handle write/suspend/commit/resume sequence.
In few places this properly handle vg_revert() after suspend failure,
and also ensures there is metadata backup after successful vg_commit().
When repairing RAID LVs that have multiple PVs per image, allow
replacement images to be reallocated from the PVs that have not
failed in the image if there is sufficient space.
This allows for scenarios where a 2-way RAID1 is spread across 4 PVs,
where each image lives on two PVs but doesn't use the entire space
on any of them. If one PV fails and there is sufficient space on the
remaining PV in the image, the image can be reallocated on just the
remaining PV.
I've changed build_parallel_areas_from_lv to take a new parameter
that allows the caller to build parallel areas by LV vs by segment.
Previously, the function created a list of parallel areas for each
segment in the given LV. When it came time for allocation, the
parallel areas were honored on a segment basis. This was problematic
for RAID because any new RAID image must avoid being placed on any
PVs used by other images in the RAID. For example, if we have a
linear LV that has half its space on one PV and half on another, we
do not want an up-convert to use either of those PVs. It should
especially not wind up with the following, where the first portion
of one LV is paired up with the second portion of the other:
------PV1------- ------PV2-------
[ 2of2 image_1 ] [ 1of2 image_1 ]
[ 1of2 image_0 ] [ 2of2 image_0 ]
---------------- ----------------
Previously, it was possible for this to happen. The change makes
it so that the returned parallel areas list contains one "super"
segment (seg_pvs) with a list of all the PVs from every actual
segment in the given LV and covering the entire logical extent range.
This change allows RAID conversions to function properly when there
are existing images that contain multiple segments that span more
than one PV.
When down-converting a RAID1 LV, if the user specifies too few devices,
they will get a confusing message.
Ex:
[root]# lvcreate -m 2 --type raid1 -n raid -L 500M taft
Logical volume "raid" created
[root]# lvconvert -m 0 taft/raid /dev/sdd1
Unable to extract enough images to satisfy request
Failed to extract images from taft/raid
This patch makes the error message a bit clearer by telling the user
the count they are trying to remove and the number of devices they
supplied.
[root@bp-01 lvm2]# lvcreate --type raid1 -m 3 -L 200M -n lv vg
Logical volume "lv" created
[root@bp-01 lvm2]# lvconvert -m -3 vg/lv /dev/sdb1
Unable to remove 3 images: Only 1 device given.
Failed to extract images from vg/lv
[root@bp-01 lvm2]# lvconvert -m -3 vg/lv /dev/sd[bc]1
Unable to remove 3 images: Only 2 devices given.
Failed to extract images from vg/lv
[root@bp-01 lvm2]# lvconvert -m -3 vg/lv /dev/sd[bcd]1
[root@bp-01 lvm2]# lvs -a -o name,attr,devices vg
LV Attr Devices
lv -wi-a----- /dev/sde1(1)
This patch doesn't work in all cases. The user can specify the right
number of devices, but not a sufficient amount of devices from the LV.
This will produce the old error message:
[root@bp-01 lvm2]# lvconvert -m -3 vg/lv /dev/sd[bcf]1
Unable to extract enough images to satisfy request
Failed to extract images from vg/lv
However, I think this error message is sufficient for this case.
Introduce a new parameter called "approx_alloc" that is set when the
desired size of a new LV is specified in percentage terms. If set,
the allocation code tries to get as much space as it can but does not
fail if can at least get some.
One of the practical implications is that users can now specify 100%FREE
when creating RAID LVs, like this:
~> lvcreate --type raid5 -i 2 -l 100%FREE -n lv vg
Optimize and cleanup recently introduced new function wipe_lv.
Use compound literals to get nicely initialized wipe_params struct.
Pass in lv as explicit argument for wipe_lv.
Use cmd from lv structure.
Initialize only non-null members so it's easy to see what
is the special arg.
Use common wipe_lv (former set_lv) fn to do zeroing as well as signature
wiping if needed. Provide new struct wipe_lv_params to define the
functionality.
Bind "lvcreate -W/--wipesignatures y" with proper wipe_lv call.
Also, add "yes" and "force" to lvcreate_params so it's possible
to apply them for the prompt: "WARNING: %s detected on %s. Wipe it? [y/n]".
Creation, deletion, [de]activation, repair, conversion, scrubbing
and changing operations are all now available for RAID LVs in a
cluster - provided that they are activated exclusively.
The code has been changed to ensure that no LV or sub-LV activation
is attempted cluster-wide. This includes the often overlooked
operations of activating metadata areas for the brief time it takes
to clear them. Additionally, some 'resume_lv' operations were
replaced with 'activate_lv_excl_local' when sub-LVs were promoted
to top-level LVs for removal, clearing or extraction. This was
necessary because it forces the appropriate renaming actions the
occur via resume in the single-machine case, but won't happen in
a cluster due to the necessity of acquiring a lock first.
The *raid* tests have been updated to allow testing in a cluster.
For the most part, this meant creating devices with '-aey' if they
were to be converted to RAID. (RAID requires the converting LV to
be EX because it is a condition of activation for the RAID LV in
a cluster.)
When images and their associated metadata are removed from a RAID1 LV,
the remaining sub-LVs are "shifted" down to fill the gaps. For
example, if there is a 3-way mirror:
[0][1][2]
and we remove device#0, the devices will be shifted down
[1][2]
and renamed.
[0][1]
This can create a problem for resume_lv (specifically,
dm_tree_activate_children) during the renaming process though. This
is because it will attempt to rename the higher indexed sub-LVs first
and find that it cannot because there are currently other sub-LVs with
that name. The solution is to check for a conflicting name before
attempting to rename. If a conflict is found and that conflicting
sub-LV is also in the process of renaming, we can defer the current
rename until the conflicting sub-LV has renamed and cleared the
conflict.
Now that resume_lv can handle these types of rename conflicts, we can
remove the workaround in RAID that was attempting to resume a RAID1
LV from the bottom-up in order to force a proper rename in assending
order before attempting a resume on the top-level LV. This "hack"
only worked for single machine use-cases of LVM. Clearing this up
paves the way for exclusive activation of RAID LVs in a cluster.
The function 'get_pv_list_for_lv' will assemble all the PVs that are
used by the specified LV. It uses 'for_each_sub_lv' to traverse all
of the sub-lvs which may compose it.
There are places where 'lv_is_active' was being used where it was
more correct to use 'lv_is_active_locally'. For example, when checking
for the existance of a kernel instance before asking for its status.
Most of the time these would work correctly. (RAID is only allowed on
non-clustered VGs at the moment, which means that 'lv_is_active' and
'lv_is_active_locally' would give the same result.) However, it is
more correct to use the proper variant and it helps with future
scenarios where targets might be allowed exclusively (or clustered) in
a cluster VG.
