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I've updated the dm_status_raid structure and dm_get_status_raid()
function to make it handle the new kernel status fields that will
be coming in dm-raid v1.5.0. It is backwards compatible with the
old status line - initializing the new fields to '0'. The new
structure is also more amenable to future changes. It includes a
'reserved' field that is currently initialized to zero but could
be used to hold flags describing new features. It also now uses
pointers for the character strings instead of attempting to allocate
their space along with the structure (causing the size of the
structure to be variable). This allows future fields to be appended.
The new fields that are available are:
- sync_action : shows what the sync thread in the kernel is doing
(idle, frozen, resync, recover, check, repair, or
reshape)
- mismatch_count: shows the number of discrepancies which were
found or repaired by a "check" or "repair"
process, respectively.
Previous commit included changes to WHATSNEW, but the code changes
were missing. Here is the description from the previous commit:
commit bbc6378b73
Author: Jonathan Brassow <jbrassow@redhat.com>
Date: Thu Feb 21 11:31:36 2013 -0600
RAID: Make 'lvchange --refresh' restore transiently failed RAID PVs
A new function (dm_tree_node_force_identical_table_reload) was added to
avoid the suppression of identical table reloads. This allows RAID LVs
to reload the on-disk superblock information that contains which devices
have failed and the bitmaps. If the failed device has returned, this has
the effect of restoring the device and initiating recovery. Without this
patch, the user had to completely deactivate their RAID LV and re-activate
it in order to restore the failed device. Now they simply need to
suspend and resume (which is done by 'lvchange --refresh').
The identical table suppression is only avoided if the LV is not PARTAIL
(i.e. all of it's devices can be seen and read by LVM) and the kernel
status of the array contains failed devices. In other words, the function
will only be called in the case where we may have success in restoring
a failed device in the array.
Similar to the way thin* accesses its kernel status, we add a method
for RAID to grab the various values in its status output without the
higher levels (LVM) having to understand how to parse the output.
Added functions include:
- lib/activate/dev_manager.c:dev_manager_raid_status()
Pulls the status line from the kernel
- libdm/libdm-deptree.c:dm_get_status_raid()
Parses status line and puts components into dm_status_raid struct
- lib/activate/activate.c:lv_raid_dev_health()
Accesses dm_status_raid to deliver raid dev_health string
The new structure and functions can provide a more unified way to access
status information. ('lv_raid_percent' could switch to using these
functions, for example.)
If the resume of preloaded node fails, do not leave such
node in the table - since it may not be easy to detach such
node later when the node is i.e. internal.
i.e. failing activation of the thin pool with mismatching
chunk size may leave -tpool device in the table, which
could have been then removed only by dmsetup command.
Patch clears the flag if thin pool is stacked over mirror.
Since thin pool could be used to stack device over mirrors,
it needs resume properly i.e. mirrors with corelog which are otherwise
unconditionally skipped (for pvmove functionality).
This patch adds support for RAID10. It is not the default at this
stage. The user needs to specify '--type raid10' if they would like
RAID10 instead of stacked mirror over stripe.
if the thin_check fail on thin pool - still return successful deactivation,
since lvremove would currently fail.
TODO: find some way to not run check with lvremove.
Add some hack math to allow 16GB devices to be passed as thinpool metadata.
Since kernel has put in limit to not allow which are just bigger then
some predefined constant in kernel but not matching 16GB so any device bigger
is rejected.
FIXME: Current code still might need more tweaks to be more generic.
It was not possible to pass down the DM_[FORCE|NO]SYNC flags to
'dm_tree_node_add_raid_target'. This meant that converting to 'raid1' from
'mirror' would cause a full resync. (It also meant that '--nosync' was
ineffective when creating a 'raid1' LV.)
I've taken the 'reserved' parameter in 'dm_tree_node_add_raid_target' and
used it for the "flags" parameter. Now it is possible to pass the sync
flags and any other flags that may come up.
Using PRELOAD part would lead to problems when the problem
would happen before vg_write and vg_commit.
Also this change is necessary for snapshot creation sequence.
LVM- prefix.
Try harder not to leave stray empty devices around (locally or remotely) when
reverting changes after failures while there are inactive tables.
Add dm_get_status_thin_pool and dm_get_status_thin functions to
parse 'params' argument which is received via dm_get_next_target.
Returns filed structure allocated from given mempool.
Remove DM_THIN_ERROR_DEVICE_ID from API.
Remove API warning.
Drop code that was using DM_THIN_ERROR_DEVICE_ID (already commented)
Remove debug message which slipped in through some previous commit.
A little code shuffling and adding support for
DM_THIN_ERROR_DEVICE_ID which might be eventually be used
for activation of thin which is going to be deleted.
For now we do not need it lvm.
Add a new node flag send_messages that is used to simplify
test when to call _node_send_messages().
Add call to _node_send_messages when pool is deeper in the tree.
There should be no need for retry for our internal devices - it would be hinding
our own bug in the tree processing.
Update error messages to show also also device name.
No WHATS_NEW - in release fix.
Certain errno codes could be expected in some situations thus
add experimental support for them.
When expected errno is set after ioctl error - function skips error
printing and exits succefully.
Currently only useful for thin pool messages.
The current code does not always assign proper udev flags to sub-LVs (e.g.
mirror images and log LVs). This shows up especially during a splitmirror
operation in which an image is split off from a mirror to form a new LV.
A mirror with a disk log is actually composed of 4 different LVs: the 2
mirror images, the log, and the top-level LV that "glues" them all together.
When a 2-way mirror is split into two linear LVs, two of those LVs must be
removed. The segments of the image which is not split off to form the new
LV are transferred to the top-level LV. This is done so that the original
LV can maintain its major/minor, UUID, and name. The sub-lv from which the
segments were transferred gets an error segment as a transitory process
before it is eventually removed. (Note that if the error target was not put
in place, a resume_lv would result in two LVs pointing to the same segment!
If the machine crashes before the eventual removal of the sub-LV, the result
would be a residual LV with the same mapping as the original (now linear) LV.)
So, the two LVs that need to be removed are now the log device and the sub-LV
with the error segment. If udev_flags are not properly set, a resume will
cause the error LV to come up and be scanned by udev. This causes I/O errors.
Additionally, when udev scans sub-LVs (or former sub-LVs), it can cause races
when we are trying to remove those LVs. This is especially bad during failure
conditions.
When the mirror is suspended, the top-level along with its sub-LVs are
suspended. The changes (now 2 linear devices and the yet-to-be-removed log
and error LV) are committed. When the resume takes place on the original
LV, there are no longer links to the other sub-lvs through the LVM metadata.
The links are implicitly handled by querying the kernel for a list of
dependencies. This is done in the '_add_dev' function (which is recursively
called for each dependency found) - called through the following chain:
_add_dev
dm_tree_add_dev_with_udev_flags
<*** DM / LVM divide ***>
_add_dev_to_dtree
_add_lv_to_dtree
_create_partial_dtree
_tree_action
dev_manager_activate
_lv_activate_lv
_lv_resume
lv_resume_if_active
When udev flags are calculated by '_get_udev_flags', it is done by referencing
the 'logical_volume' structure. Those flags are then passed down into
'dm_tree_add_dev_with_udev_flags', which in turn passes them to '_add_dev'.
Unfortunately, when '_add_dev' is finding the dependencies, it has no way to
calculate their proper udev_flags. This is because it is below the DM/LVM
divide - it doesn't have access to the logical_volume structure. In fact,
'_add_dev' simply reuses the udev_flags given for the initial device! This
virtually guarentees the udev_flags are wrong for all the dependencies unless
they are reset by some other mechanism. The current code provides no such
mechanism. Even if '_add_new_lv_to_dtree' were called on the sub-devices -
which it isn't - entries already in the tree are simply passed over, failing
to reset any udev_flags. The solution must retain its implicit nature of
discovering dependencies and be able to go back over the dependencies found
to properly set the udev_flags.
My solution simply calls a new function before leaving '_add_new_lv_to_dtree'
that iterates over the dtree nodes to properly reset the udev_flags of any
children. It is important that this function occur after the '_add_dev' has
done its job of querying the kernel for a list of dependencies. It is this
list of children that we use to look up their respective LVs and properly
calculate the udev_flags.
This solution has worked for single machine, cluster, and cluster w/ exclusive
activation.
Make limits for thin data_block_size and device_id part of public API.
FIXME: read them possible from some kernel header file in the future ?
But we may need to support different values for different versions ?
Before, we used to display "Can't remove open logical volume" which was
generic. There 3 possibilities of how a device could be opened:
- used by another device
- having a filesystem on that device which is mounted
- opened directly by an application
With the help of sysfs info, we can distinguish the first two situations.
The third one will be subject to "remove retry" logic - if it's opened
quickly (e.g. a parallel scan from within a udev rule run), this will
finish quickly and we can remove it once it has finished. If it's a
legitimate application that keeps the device opened, we'll do our best
to remove the device, but we will fail finally after a few retries.
This patch adds the ability to upconvert a raid1 array - say from 2-way to
3-way. It does not yet support upconverting linear to n-way.
The 'raid' device-mapper target allows for individual components (images) of
an array to be specified for rebuild. This mechanism is used when adding
new images to the array so that the new images can be resync'ed while the
rest of the images in the array can remain 'in-sync'. (There is no
mirror-on-mirror layering required.)
~> lvconvert --splitmirrors 1 --trackchanges vg/lv
The '--trackchanges' option allows a user the ability to use an image of
a RAID1 array for the purposes of temporary read-only access. The image
can be merged back into the array at a later time and only the blocks that
have changed in the array since the split will be resync'ed. This
operation can be thought of as a partial split. The image is never completely
extracted from the array, in that the array reserves the position the device
occupied and tracks the differences between the array and the split image via
a bitmap. The image itself is rendered read-only and the name (<LV>_rimage_*)
cannot be changed. The user can complete the split (permanently splitting the
image from the array) by re-issuing the 'lvconvert' command without the
'--trackchanges' argument and specifying the '--name' argument.
~> lvconvert --splitmirrors 1 --name my_split vg/lv
Merging the tracked image back into the array is done with the '--merge'
option (included in a follow-on patch).
~> lvconvert --merge vg/lv_rimage_<n>
The internal mechanics of this are relatively simple. The 'raid' device-
mapper target allows for the specification of an empty slot in an array
via '- -'. This is what will be used if a partial activation of an array
is ever required. (It would also be possible to use 'error' targets in
place of the '- -'.) If a RAID image is found to be both read-only and
visible, then it is considered separate from the array and '- -' is used
to hold it's position in the array. So, all that needs to be done to
temporarily split an image from the array /and/ cause the kernel target's
bitmap to track (aka "mark") changes made is to make the specified image
visible and read-only. To merge the device back into the array, the image
needs to be returned to the read/write state of the top-level LV and made
invisible.
Implementation described in doc/lvm2-raid.txt.
Basic support includes:
- ability to create RAID 1/4/5/6 arrays
- ability to delete RAID arrays
- ability to display RAID arrays
Notable missing features (not included in this patch):
- ability to clean-up/repair failures
- ability to convert RAID segment types
- ability to monitor RAID segment types
When some target is passing empty parameters to some dm target,
report this as an internal error to better catch some broken
table construction (some mirror conversions seem to be doing
this for now).
This fn calls rm_dev_node directly - an exceptional case. It needs to check
the DM_UDEV_DISABLE_LIBRARY_FALLBACK flag directly (it's called in dm_task_run
normally where it's checked already).
and use this for the LVM critical section logic. Also report an error if
code tries to load a table while any device is known to be in the
suspended state.
(If the variety of problems these changes are showing up can't be fixed
before the next release, the error messages can be reduced to debug
level.)
are affected by the move. (Currently it's possible for I/O to become
trapped between suspended devices amongst other problems.
The current fix was selected so as to minimise the testing surface. I
hope eventually to replace it with a cleaner one that extends the
deptree code.
Some lvconvert scenarios still suffer from related problems.
