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The copy of VG metadata stored in lvmcache was not being used
in general. It pretended to be a generic VG metadata cache,
but was not being used except for clvmd activation. There
it was used to avoid reading from disk while devices were
suspended, i.e. in resume.
This removes the code that attempted to make this look
like a generic metadata cache, and replaces with with
something narrowly targetted to what it's actually used for.
This is a way of passing the VG from suspend to resume in
clvmd. Since in the case of clvmd one caller can't simply
pass the same VG to both suspend and resume, suspend needs
to stash the VG somewhere that resume can grab it from.
(resume doesn't want to read it from disk since devices
are suspended.) The lvmcache vginfo struct is used as a
convenient place to stash the VG to pass it from suspend
to resume, even though it isn't related to the lvmcache
or vginfo. These suspended_vg* vginfo fields should
not be used or touched anywhere else, they are only to
be used for passing the VG data from suspend to resume
in clvmd. The VG data being passed between suspend and
resume is never modified, and will only exist in the
brief period between suspend and resume in clvmd.
suspend has both old (current) and new (precommitted)
copies of the VG metadata. It stashes both of these in
the vginfo prior to suspending devices. When vg_commit
is successful, it sets a flag in vginfo as before,
signaling the transition from old to new metadata.
resume grabs the VG stashed by suspend. If the vg_commit
happened, it grabs the new VG, and if the vg_commit didn't
happen it grabs the old VG. The VG is then used to resume
LVs.
This isolates clvmd-specific code and usage from the
normal lvm vg_read code, making the code simpler and
the behavior easier to verify.
Sequence of operations:
- lv_suspend() has both vg_old and vg_new
and stashes a copy of each onto the vginfo:
lvmcache_save_suspended_vg(vg_old);
lvmcache_save_suspended_vg(vg_new);
- vg_commit() happens, which causes all clvmd
instances to call lvmcache_commit_metadata(vg).
A flag is set in the vginfo indicating the
transition from the old to new VG:
vginfo->suspended_vg_committed = 1;
- lv_resume() needs either vg_old or vg_new
to use in resuming LVs. It doesn't want to
read the VG from disk since devices are
suspended, so it gets the VG stashed by
lv_suspend:
vg = lvmcache_get_suspended_vg(vgid);
If the vg_commit did not happen, suspended_vg_committed
will not be set, and in this case, lvmcache_get_suspended_vg()
will return the old VG instead of the new VG, and it will
resume LVs based on the old metadata.
Make lvm2_disable_dmeventd_monitoring() more explicit.
As memlock_inc_daemon() is also used by clvmd, which
does changes dmeventd and suspend ignore state at
some stages - make updates of these 2 variable
tied to the call of lvm2_disable_dmeventd_monitoring().
Once this call is made dmeventd monitoring
and suspended devices are ignored.
TODO: all lvm-global settings should really be moved
to command context.
Just like MD filtering that detects components of software RAID (md),
add detection for firmware RAID.
We're not adding any native code to detect this - there are lots of
firmware RAIDs out there which is just out of LVM scope. However,
with current changes with which we're able to get device info from
external sources (e.g. external_device_info_source="udev"), we can
do this easily if the external device status source has this kind
of information - which is the case of "udev" source where the results
of blkid scans are stored.
This detection should cover all firmware RAIDs that blkid can detect and
which are identified as:
ID_FS_TYPE = {adaptec,ddf,hpt45x,hpt37x,isw,jmicron,lsi_mega,nvidia,promise_fasttrack,silicon_medley,via}_raid_member
There is a problem with the way mirrors have been designed to handle
failures that is resulting in stuck LVM processes and hung I/O. When
mirrors encounter a write failure, they block I/O and notify userspace
to reconfigure the mirror to remove failed devices. This process is
open to a couple races:
1) Any LVM process other than the one that is meant to deal with the
mirror failure can attempt to read the mirror, fail, and block other
LVM commands (including the repair command) from proceeding due to
holding a lock on the volume group.
2) If there are multiple mirrors that suffer a failure in the same
volume group, a repair can block while attempting to read the LVM
label from one mirror while trying to repair the other.
Mitigation of these races has been attempted by disallowing label reading
of mirrors that are either suspended or are indicated as blocking by
the kernel. While this has closed the window of opportunity for hitting
the above problems considerably, it hasn't closed it completely. This is
because it is still possible to start an LVM command, read the status of
the mirror as healthy, and then perform the read for the label at the
moment after a the failure is discovered by the kernel.
I can see two solutions to this problem:
1) Allow users to configure whether mirrors can be candidates for LVM
labels (i.e. whether PVs can be created on mirror LVs). If the user
chooses to allow label scanning of mirror LVs, it will be at the expense
of a possible hang in I/O or LVM processes.
2) Instrument a way to allow asynchronous label reading - allowing
blocked label reads to be ignored while continuing to process the LVM
command. This would action would allow LVM commands to continue even
though they would have otherwise blocked trying to read a mirror. They
can then release their lock and allow a repair command to commence. In
the event of #2 above, the repair command already in progress can continue
and repair the failed mirror.
This patch brings solution #1. If solution #2 is developed later on, the
configuration option created in #1 can be negated - allowing mirrors to
be scanned for labels by default once again.
Add log/debug_classes to lvm.conf to allow debug messages to be
classified and filtered at runtime.
The dm_errno field is only used by log_error(), so I've redefined it
for log_debug() messages to hold the message class.
By default, all existing messages appear, but we can add categories that
generate high volumes of data, such as logging all traffic to/from
lvmetad.
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.
Add config option to enable crc checking of VG structures.
Currently it's disabled by default.
For the internal test-suite this check it is enabled.
Note: In the case the internal error is detected, debug build with
compile option DEBUG_ENFORCE_POOL_LOCKING helps to catch the source
of the problem.
Also, add a new 'obtain_device_list_from_udev' setting to lvm.conf with which
we can turn this feature on or off if needed.
If set, the cache of block device nodes with all associated symlinks
will be constructed out of the existing udev database content.
This avoids using and opening any inapplicable non-block devices or
subdirectories found in the device directory. This setting is applied
to udev-managed device directory only, other directories will be scanned
fully. LVM2 needs to be compiled with udev support for this setting to
take effect. N.B. Any device node or symlink not managed by udev in
udev directory will be ignored with this setting on.
Add configurable option to define minimal size of
of block device usable as a PV.
pv_min_size() is added to lvm-globals and it's being
initialized through _process_config.
Macro PV_MIN_SIZE is unused and removed.
New define DEFAULT_PV_MIN_SIZE_KB is added to lvm-global
and unlike PV_MIN_SIZE it uses KB units.
Should help users with various slow devices attached to the system,
which cannot be easily filtered out (like FDD on /dev/sdX):
https://bugzilla.redhat.com/show_bug.cgi?id=644578
We can already detect MD devices internally. But when using MD partitions,
these have "block extended major" (blkext) assigned (259). Blkext major
is also used in general, so we need to check whether the original device
is an MD device actually.
the background polldaemon is allowed to start. It can be used
standalone or in conjunction with --refresh or --available y.
Control over when the background polldaemon starts will be particularly
important for snapshot-merge of a root filesystem.
Dracut will be updated to activate all LVs with: --poll n
The lvm2-monitor initscript will start polling with: --poll y
NOTE: Because we currently have no way of knowing if a background
polldaemon is active for a given LV the following limitations exist and
have been deemed acceptable:
1) it is not possible to stop an active polldaemon; so the lvm2-monitor
initscript doesn't stop running polldaemon(s)
2) redundant polldaemon instances will be started for all specified LVs
if vgchange or lvchange are repeatedly used with '--poll y'
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Very simple / crude method of removing 'is_static' from initialization.
Why should we require an application tell us whether it is linked
statically or dynamically to libLVM? If the application is linked
statically, but libraries exist and dlopen() calls succeed, why
do we care if it's statically linked?
