IF YOU WOULD LIKE TO GET AN ACCOUNT, please write an
email to Administrator. User accounts are meant only to access repo
and report issues and/or generate pull requests.
This is a purpose-specific Git hosting for
BaseALT
projects. Thank you for your understanding!
Только зарегистрированные пользователи имеют доступ к сервису!
Для получения аккаунта, обратитесь к администратору.
The fact that vg repair is implemented as a part of vg read
has led to a messy and complicated implementation of vg_read,
and limited and uncontrolled repair capability. This splits
read and repair apart.
Summary
-------
- take all kinds of various repairs out of vg_read
- vg_read no longer writes anything
- vg_read now simply reads and returns vg metadata
- vg_read ignores bad or old copies of metadata
- vg_read proceeds with a single good copy of metadata
- improve error checks and handling when reading
- keep track of bad (corrupt) copies of metadata in lvmcache
- keep track of old (seqno) copies of metadata in lvmcache
- keep track of outdated PVs in lvmcache
- vg_write will do basic repairs
- new command vgck --updatemetdata will do all repairs
Details
-------
- In scan, do not delete dev from lvmcache if reading/processing fails;
the dev is still present, and removing it makes it look like the dev
is not there. Records are now kept about the problems with each PV
so they be fixed/repaired in the appropriate places.
- In scan, record a bad mda on failure, and delete the mda from
mda in use list so it will not be used by vg_read or vg_write,
only by repair.
- In scan, succeed if any good mda on a device is found, instead of
failing if any is bad. The bad/old copies of metadata should not
interfere with normal usage while good copies can be used.
- In scan, add a record of old mdas in lvmcache for later, do not repair
them while reading, and do not let them prevent us from finding and
using a good copy of metadata from elsewhere. One result is that
"inconsistent metadata" is no longer a read error, but instead a
record in lvmcache that can be addressed separate from the read.
- Treat a dev with no good mdas like a dev with no mdas, which is an
existing case we already handle.
- Don't use a fake vg "handle" for returning an error from vg_read,
or the vg_read_error function for getting that error number;
just return null if the vg cannot be read or used, and an error_flags
arg with flags set for the specific kind of error (which can be used
later for determining the kind of repair.)
- Saving an original copy of the vg metadata, for purposes of reverting
a write, is now done explicitly in vg_read instead of being hidden in
the vg_make_handle function.
- When a vg is not accessible due to "access restrictions" but is
otherwise fine, return the vg through the new error_vg arg so that
process_each_pv can skip the PVs in the VG while processing.
(This is a temporary accomodation for the way process_each_pv
tracks which devs have been looked at, and can be dropped later
when process_each_pv implementation dev tracking is changed.)
- vg_read does not try to fix or recover a vg, but now just reads the
metadata, checks access restrictions and returns it.
(Checking access restrictions might be better done outside of vg_read,
but this is a later improvement.)
- _vg_read now simply makes one attempt to read metadata from
each mda, and uses the most recent copy to return to the caller
in the form of a 'vg' struct.
(bad mdas were excluded during the scan and are not retried)
(old mdas were not excluded during scan and are retried here)
- vg_read uses _vg_read to get the latest copy of metadata from mdas,
and then makes various checks against it to produce warnings,
and to check if VG access is allowed (access restrictions include:
writable, foreign, shared, clustered, missing pvs).
- Things that were previously silently/automatically written by vg_read
that are now done by vg_write, based on the records made in lvmcache
during the scan and read:
. clearing the missing flag
. updating old copies of metadata
. clearing outdated pvs
. updating pv header flags
- Bad/corrupt metadata are now repaired; they were not before.
Test changes
------------
- A read command no longer writes the VG to repair it, so add a write
command to do a repair.
(inconsistent-metadata, unlost-pv)
- When a missing PV is removed from a VG, and then the device is
enabled again, vgck --updatemetadata is needed to clear the
outdated PV before it can be used again, where it wasn't before.
(lvconvert-repair-policy, lvconvert-repair-raid, lvconvert-repair,
mirror-vgreduce-removemissing, pv-ext-flags, unlost-pv)
Reading bad/old metadata
------------------------
- "bad metadata": the mda_header or metadata text has invalid fields
or can't be parsed by lvm. This is a form of corruption that would
not be caused by known failure scenarios. A checksum error is
typically included among the errors reported.
- "old metadata": a valid copy of the metadata that has a smaller seqno
than other copies of the metadata. This can happen if the device
failed, or io failed, or lvm failed while commiting new metadata
to all the metadata areas. Old metadata on a PV that has been
removed from the VG is the "outdated" case below.
When a VG has some PVs with bad/old metadata, lvm can simply ignore
the bad/old copies, and use a good copy. This is why there are
multiple copies of the metadata -- so it's available even when some
of the copies cannot be used. The bad/old copies do not have to be
repaired before the VG can be used (the repair can happen later.)
A PV with no good copies of the metadata simply falls back to being
treated like a PV with no mdas; a common and harmless configuration.
When bad/old metadata exists, lvm warns the user about it, and
suggests repairing it using a new metadata repair command.
Bad metadata in particular is something that users will want to
investigate and repair themselves, since it should not happen and
may indicate some other problem that needs to be fixed.
PVs with bad/old metadata are not the same as missing devices.
Missing devices will block various kinds of VG modification or
activation, but bad/old metadata will not.
Previously, lvm would attempt to repair bad/old metadata whenever
it was read. This was unnecessary since lvm does not require every
copy of the metadata to be used. It would also hide potential
problems that should be investigated by the user. It was also
dangerous in cases where the VG was on shared storage. The user
is now allowed to investigate potential problems and decide how
and when to repair them.
Repairing bad/old metadata
--------------------------
When label scan sees bad metadata in an mda, that mda is removed
from the lvmcache info->mdas list. This means that vg_read will
skip it, and not attempt to read/process it again. If it was
the only in-use mda on a PV, that PV is treated like a PV with
no mdas. It also means that vg_write will also skip the bad mda,
and not attempt to write new metadata to it. The only way to
repair bad metadata is with the metadata repair command.
When label scan sees old metadata in an mda, that mda is kept
in the lvmcache info->mdas list. This means that vg_read will
read/process it again, and likely see the same mismatch with
the other copies of the metadata. Like the label_scan, the
vg_read will simply ignore the old copy of the metadata and
use the latest copy. If the command is modifying the vg
(e.g. lvcreate), then vg_write, which writes new metadata to
every mda on info->mdas, will write the new metadata to the
mda that had the old version. If successful, this will resolve
the old metadata problem (without needing to run a metadata
repair command.)
Outdated PVs
------------
An outdated PV is a PV that has an old copy of VG metadata
that shows it is a member of the VG, but the latest copy of
the VG metadata does not include this PV. This happens if
the PV is disconnected, vgreduce --removemissing is run to
remove the PV from the VG, then the PV is reconnected.
In this case, the outdated PV needs have its outdated metadata
removed and the PV used flag needs to be cleared. This repair
will be done by the subsequent repair command. It is also done
if vgremove is run on the VG.
MISSING PVs
-----------
When a device is missing, most commands will refuse to modify
the VG. This is the simple case. More complicated is when
a command is allowed to modify the VG while it is missing a
device.
When a VG is written while a device is missing for one of it's PVs,
the VG metadata is written to disk with the MISSING flag on the PV
with the missing device. When the VG is next used, it is treated
as if the PV with the MISSING flag still has a missing device, even
if that device has reappeared.
If all LVs that were using a PV with the MISSING flag are removed
or repaired so that the MISSING PV is no longer used, then the
next time the VG metadata is written, the MISSING flag will be
dropped.
Alternative methods of clearing the MISSING flag are:
vgreduce --removemissing will remove PVs with missing devices,
or PVs with the MISSING flag where the device has reappeared.
vgextend --restoremissing will clear the MISSING flag on PVs
where the device has reappeared, allowing the VG to be used
normally. This must be done with caution since the reappeared
device may have old data that is inconsistent with data on other PVs.
Bad mda repair
--------------
The new command:
vgck --updatemetadata VG
first uses vg_write to repair old metadata, and other basic
issues mentioned above (old metadata, outdated PVs, pv_header
flags, MISSING_PV flags). It will also go further and repair
bad metadata:
. text metadata that has a bad checksum
. text metadata that is not parsable
. corrupt mda_header checksum and version fields
(To keep a clean diff, #if 0 is added around functions that
are replaced by new code. These commented functions are
removed by the following commit.)
The lvm fullreport works per VG and as such, the vg, lv, pv, seg and
pvseg subreport is done for each VG. However, if the PV is not part of
any VG yet, we still want to display pv and pvseg subreports for these
"orphan" PVs - so enable this for lvm fullreport's process_each_vg call.
If there's parent processing handle, we don't need to create completely
new report group and status report - we'll just reuse the one already
initialized for the parent.
Currently, the situation where this matter is when doing internal report
to do the selection for processing commands where we have parent processing
handle for the command itself and processing handle for the selection
part (that is selection for non-reporting tools).
Pass the single vgname as a new process_each_vg arg
instead of setting a cmd flag to tell process_each_vg
to take only the first vgname arg from argv.
Other commands with different argv formats will be
able to use it this way.
It's cleaner this way - do not mix static and dynamic
(init_processing_handle) initializers. Use the dynamic one everywhere.
This makes it easier to manage the code - there are no "exceptions"
then and we don't need to take care about two ways of initializing the
same thing - just use one common initializer throughout and it's clear.
Also, add more comments, mainly in the report_for_selection fn explaining
what is being done and why with respect to the processing_handle and
selection_handle.
Call _init_processing_handle, _init_selection_handle and
_destroy_processing_handle in process_each_* and related functions to
set up and destroy handles used while processing items.
This patch replaces "void *handle" with "struct processing_handle *handle"
in process_each_*, process_single_* and related functions.
The struct processing_handle consists of two handles inside now:
- the "struct selection_handle *selection_handle" used for
applying selection criteria while processing process_each_*,
process_single_* and related functions (patches using this
logic will follow)
- the "void* custom_handle" (this is actually the original handle
used before this patch - a pointer to custom data passed into
process_each_*, process_single_* and related functions).
Accept -q as the short form of --quiet.
Suppress non-essential standard output if -q is given twice.
Treat log/silent in lvm.conf as equivalent to -qq.
Review all log_print messages and change some to
log_print_unless_silent.
When silent, the following commands still produce output:
dumpconfig, lvdisplay, lvmdiskscan, lvs, pvck, pvdisplay,
pvs, version, vgcfgrestore -l, vgdisplay, vgs.
[Needs checking.]
Non-essential messages are shifted from log level 4 to log level 5
for syslog and lvm2_log_fn purposes.
Remove the checks for vg_read_error() in most of the tools callback
functions and instead make the check in _process_one_vg() more general.
In all but vgcfgbackup, we do not want to proceed if we get any error
from vg_read(). In vgcfgbackup's case, we may proceed if the backup
is to proceed with inconsistent VGs. This is a special case though,
and we mark it with the READ_ALLOW_INCONSISTENT flag passed to
process_each_vg (and subsequently to _process_one_vg).
NOTE: More cleanup is needed in the vg_read_error() path cases.
This patch is a start.
In vg_backup_single, we should error out if we vg_read_error(vg) and the
error code we received was anything other than FAILED_INCONSISTENT.
Original code contained an error because C operator precedence.
Note - this was part of the vg_read() so no WHATS_NEW entry neceesary.
Author: Dave Wysochanski <dwysocha@redhat.com>
Sun May 3 12:32:30 CEST 2009 Petr Rockai <me@mornfall.net>
* Rework the toollib interface (process_each_*) on top of new vg_read.
Rebased 6/26/09 by Dave W.
- Add skipping message to process_each_lv
- Remove inconsistent_t.
Several commands calls process_each_vg() and in provided
callback it explicitly recovers VG if inconsistent.
(vgchange, vgconvert, vgscan)
It means that old VG is released and reread but the function
above (process_one_vg) tries to unlock and release old VG.
Patch moves the repair logic into _process_one_vg() function.
It always tries to read vg (even inconsistent) and then decides
what to do according new defined parameter.
Also patch unifies inconsistent error messages.
The only slight change if for vgremove command, where
it now tries to repair VG before it removes if force arg is given.
(It works similar way before, just the order of operation changed).
to back this out so you can do that commit, let me know. Also, if there's
an issue with the error message that's displayed, just change it in tools.h.
This causes a "device-mapper driver/module not loaded?" error message to
be displayed for the commands that require dm-mod, if the tools can't get
the driver version. It's not done for commands that don't require dm-mod.
This should clear up some problems people have had attempting to use lvm2
without rtfm'ing.
Lots of changes/very little testing so far => there'll be bugs!
Use 'vgcreate -M text' to create a volume group with its metadata stored
in text files. Text format metadata changes should be reasonably atomic,
with a (basic) automatic recovery mechanism if the system crashes while a
change is in progress.
Add a metadata section to lvm.conf to specify multiple directories if
you want (recommended) to keep multiple copies of the metadata (eg on
different filesystems).
e.g. metadata {
dirs = ["/etc/lvm/metadata1","/usr/local/lvm/metadata2"]
}
Plenty of refinements still in the pipeline.
o Text format now has a description and time field at the top level.
o archiving and backup set the description appropriately. eg,
for an archive:
description = "Created *before* executing 'lvextend test_vg/lvol0 -l +1'."
creation_time = 1013166332
for a backup:
description = "Created *after* executing 'lvextend test_vg/lvol0 -l +1'."
creation_time = 1013166332
This is preparing the way for a simple vgcfgundo command.
is active in the device-mapper.
o Many operations can be carried out regardless of whether the VG is
active or not.
o vgscan does not activate anything - use vgchange.
o Change lvrename to support renaming of active LVs.
o Remove '//' appearing in some pathnames.
o Dummy lv_check_segments() for compilation.
