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In the past, the first 'pvscan --cache -aay dev' command
to run on the system would initialize the pvs_online dir
by scanning all devs and creating online files for all pvs
it found, and then autoactivating the VG (if complete) for
the named dev. The idea was that the system may not have
been able to run pvscan commands for early devices, so the
first pvscan to run would need to "make up" for any devices
that had appeared previously, which the system was unable to
scan. The problem or idea of making up for missed scans is
historical and should no longer be needed, so remove this
special init case.
When pvscan is run for the initialization case (the first
pvscan run on the system), it scans all devs and creates
online files for all PVs it finds. Previously it would
then autoactivate every complete VG, but change this to
only autoactive the (complete) VG corresponding to the
named device arg(s).
Fix to previous commit
"pvscan: ignore online for shared and foreign PVs"
which was incorrectly considering a PV foreign if its
VG had no system ID when the host did have a system ID.
Activation would not be allowed anyway, but we can
check for these cases early and avoid wasted time in
pvscan managing online files an attempting activation.
When a VG has multiple PVs, and all those PVs come online
at the same time, concurrent pvscans for each PV will all
create the individual pvid files, and all will often see
the VG is now complete. This causes each of the pvscan
commands to think it should activate the VG, so there
are multiple activations of the same VG. The vg lock
serializes them, and only the first pvscan actually does
the activation, but there is still a lot of extra overhead
and time used by the other pvscans that attempt to
activate the already active VG. This can lead to a backlog
of pvscans and timeouts.
To fix this, this adds a new /run/lvm/vgs_online/ dir that
works like the existing /run/lvm/pvs_online/ dir. Each pvscan
that wants to activate a VG will first try to exlusively create
the file vgs_online/<vgname>. Only the first pvscan will
succeed, and that one will do the VG activation. The other
pvscans will find the vgname file exists and will not do the
activation step.
When a PV goes offline, the vgs_online file for the corresponding
VG is removed. This allows the VG to be autoactivated again
when the PV comes online again. This requires that the vgname be
stored in the pvid files.
Use a file lock to ensure that only one pvscan will do
initialization of pvs_online, otherwise multiple concurrent
pvscans may all see an empty pvs_online directory and
do initialization.
The pvscan that is doing initialization should also only
attempt to activate complete VGs.
When aay was included in the pvscan --cache command,
the activation part was complaining about the unusual
state of the hint file since it had been recreated
just prior.
An idea from Zdenek for better ensuring valid hints by invalidating
them when pvscan --cache <device> sees a new PV, which is a case
where we know that hints should be invalidated. This is triggered
from systemd/udev logic, and there may be some cases where it would
invalidate hints that the existing methods wouldn't detect.
Save the list of PVs in /run/lvm/hints. These hints
are used to reduce scanning in a number of commands
to only the PVs on the system, or only the PVs in a
requested VG (rather than all devices on the system.)
Native disk scanning is now both reduced and
async/parallel, which makes it comparable in
performance (and often faster) when compared
to lvm using lvmetad.
Autoactivation now uses local temp files to record
online PVs, and no longer requires lvmetad.
There should be no apparent command-level change
in behavior.
When lvmetad is not used, use temporary files to record
which PVs have appeared. Use these temp files to determine
when a VG is complete, to trigger autoactivation.
This change allows us to remove lvmetad while keeping the
same autoactivation behavior that lvmetad provides.
The temp files are created in /run/lvm/pvs_online/ and are
named for the PVID of the PV. The files contain the
major:minor of the device the PV was read from.
e.g. if VG foo has dev1 and dev2, then:
. pvscan --cache -aay dev1
reads vg metadata from dev1
creates /run/lvm/pvs_online/<pvid-of-dev1>
checks if all vg->pvs are online: no
. pvscan --cache -aay dev2
reads vg metadata from dev2
creates /run/lvm/pvs_online/<pvid-of-dev2>
checks if all vg->pvs are online: yes
autoactivates vg
A 'pvscan --cache dev' (without -aay) still records that
dev is online.
A 'pvscan --cache --major X --minor Y' after a device is
gone will remove the temp file for it.
A 'pvscan --cache [-aay]' (no devs) resets the state of
temp files by removing them all, then scanning all devs
and creating temp files for PVs that are found.
If no online files exist, the first pvscan --cache scans
all devs and creates temp files for any PVs found.
The scope of the temp files is only pvscan, and they are only
used for pvscan-based autoactivation. No other commands are
concerned with or aware of these temp files. When lvm creates
or removes PVs, no attempt is made to update the temp files.
Restoring polling for activated volumes lost with my recent commit:
75fed05d3e and move start of polling
directly into _activate_lvs_in_vg() - as there we know exactly
if there was some volume even activated.
Also make it sharing same code for pvscan -aay.
Make activation commands:
vgchange -ay, lvchange -ay, pvscan -aay
take an exclusive file lock on the VG to serialize
multiple concurrent activation commands which could
otherwise interfere with each other.
As we start refactoring the code to break dependencies (see doc/refactoring.txt),
I want us to use full paths in the includes (eg, #include "base/data-struct/list.h").
This makes it more obvious when we're breaking abstraction boundaries, eg, including a file in
metadata/ from base/
Filters are still applied before any device reading or
the label scan, but any filter checks that want to read
the device are skipped and the device is flagged.
After bcache is populated, but before lvm looks for
devices (i.e. before label scan), the filters are
reapplied to the devices that were flagged above.
The filters will then find the data they need in
bcache.
There are likely more bits of code that can be removed,
e.g. lvm1/pool-specific bits of code that were identified
using FMT flags.
The vgconvert command can likely be reduced further.
The lvm1-specific config settings should probably have
some other fields set for proper deprecation.
Change run time access to the command_name struct
cmd->cname instead of indirectly through
cmd->command->cname. This removes the two run time
fields from struct command.
pvscan --cache -aay was activating LVs in exported VGs
when it should not.
It appears that this was a regression from commit 9b640c3684
"pvscan: use process_each_vg for autoactivate".
Previously, a command sent lvmetad new VG metadata in vg_commit().
In vg_commit(), devices are suspended, so any memory allocation
done by the command while sending to lvmetad, or by lvmetad while
updating its cache could deadlock if memory reclaim was triggered.
Now lvmetad is updated in unlock_vg(), after devices are resumed.
The new method for updating VG metadata in lvmetad is in two phases:
1. In vg_write(), before devices are suspended, the command sends
lvmetad a short message ("set_vg_info") telling it what the new
VG seqno will be. lvmetad sees that the seqno is newer than
the seqno of its cached VG, so it sets the INVALID flag for the
cached VG. If sending the message to lvmetad fails, the command
fails before the metadata is committed and the change is not made.
If sending the message succeeds, vg_commit() is called.
2. In unlock_vg(), after devices are resumed, the command sends
lvmetad the standard vg_update message with the new metadata.
lvmetad sees that the seqno in the new metadata matches the
seqno it saved from set_vg_info, and knows it has the latest
copy, so it clears the INVALID flag for the cached VG.
If a command fails between 1 and 2 (after committing the VG on disk,
but before sending lvmetad the new metadata), the cached VG retains
the INVALID flag in lvmetad. A subsequent command will read the
cached VG from lvmetad, see the INVALID flag, ignore the cached
copy, read the VG from disk instead, update the lvmetad copy
with the latest copy from disk, (this clears the INVALID flag
in lvmetad), and use the correct VG metadata for the command.
(This INVALID mechanism already existed for use by lvmlockd.)
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).
commit 15da467b was meant to address the case where
use_lvmetad=1 in lvm.conf, and lvmetad is not available,
in which case, pvscan --cache -aay should activate LVs.
But the commit unintentionally also changed the case
where use_lvmetad=0 in lvm.conf, in which case
pvscan --cache -aay should not activate LVs, so fix
that here.
When pvscan --cache -aay fails to connect to lvmetad it will
simply exit and do nothing. Change this so that it will
skip the lvmetad cache step and do the activation step from
disk.
