This adds the file-reflink storage driver. It is never selected
automatically for pool creation, especially not the creation of
'varlibqubes' (though it can be used if set up manually).
The code is quite small:
reflink.py lvm.py file.py + block-snapshot
sloccount 334 lines 447 (134%) 570 (171%)
Background: btrfs and XFS (but not yet ZFS) support instant copies of
individual files through the 'FICLONE' ioctl behind 'cp --reflink'.
Which file-reflink uses to snapshot VM image files without an extra
device-mapper layer. All the snapshots are essentially freestanding;
there's no functional origin vs. snapshot distinction.
In contrast to 'file'-on-btrfs, file-reflink inherently avoids
CoW-on-CoW. Which is a bigger issue now on R4.0, where even AppVMs'
private volumes are CoW. (And turning off the lower, filesystem-level
CoW for 'file'-on-btrfs images would turn off data checksums too, i.e.
protection against bit rot.)
Also in contrast to 'file', all storage features are supported,
including
- any number of revisions_to_keep
- volume.revert()
- volume.is_outdated
- online fstrim/discard
Example tree of a file-reflink pool - *-dirty.img are connected to Xen:
- /var/lib/testpool/appvms/foo/volatile-dirty.img
- /var/lib/testpool/appvms/foo/root-dirty.img
- /var/lib/testpool/appvms/foo/root.img
- /var/lib/testpool/appvms/foo/private-dirty.img
- /var/lib/testpool/appvms/foo/private.img
- /var/lib/testpool/appvms/foo/private.img@2018-01-02T03:04:05Z
- /var/lib/testpool/appvms/foo/private.img@2018-01-02T04:05:06Z
- /var/lib/testpool/appvms/foo/private.img@2018-01-02T05:06:07Z
- /var/lib/testpool/appvms/bar/...
- /var/lib/testpool/appvms/...
- /var/lib/testpool/template-vms/fedora-26/...
- /var/lib/testpool/template-vms/...
It looks similar to a 'file' pool tree, and in fact file-reflink is
drop-in compatible:
$ qvm-shutdown --all --wait
$ systemctl stop qubesd
$ sed 's/ driver="file"/ driver="file-reflink"/g' -i.bak /var/lib/qubes/qubes.xml
$ systemctl start qubesd
$ sudo rm -f /path/to/pool/*/*/*-cow.img*
If the user tries to create a fresh file-reflink pool on a filesystem
that doesn't support reflinks, qvm-pool will abort and mention the
'setup_check=no' option. Which can be passed to force a fallback on
regular sparse copies, with of course lots of time/space overhead. The
same fallback code is also used when initially cloning a VM from a
foreign pool, or from another file-reflink pool on a different
mountpoint.
'journalctl -fu qubesd' will show all file-reflink copy/rename/remove
operations on VM creation/startup/shutdown/etc.
- catch both QubesException and libvirtError - do not kill starting VM
just because an error while connecting _other_ VMs to it
- try to detach network first (and do not abort on error) - if
libvirt/libxl will manage to cleanup stale interface this way, the
attach operation below may succeed.
FixesQubesOS/qubes-issues#3163
1. Make sure VMs are started after dom0 actual memory usage is reported
to qmemman, otherwise dom0 will hold 4GB, even if just a little over 1GB
is needed at that time.
2. Request only vm.memory MB from qmemman, instead of vm.maxmem. While
HVM with PCI devices indeed do not support populate-on-demand, this is
already handled in libvirt XML.
The later may often cause VM startup fail on systems with 8GB of memory,
because maxmem is 4GB there and with dom0 keeping the other 4GB (see
point 1) there is not enough memory to start any sych VM.
FixesQubesOS/qubes-issues#3462
* qubesos/pr/187:
Don't fail create/clone if /var/lib/qubes/TYPE/NAME/ exists
Make 'qvm-volume revert' really use the latest revision
Fix wrong mocks of Volume.revisions
* qubesos/pr/185:
vm: remove doc for non-existing event `monitor-layout-change`
vm: include tag/feature name in event name
events: add support for wildcard event handlers
admin.vm.volume.ListSnapshots returned volume revisions in undefined
order, but 'qvm-volume revert' assumes the list to be in chronological
order. Make that assumption true.
* devel-20180115:
tests: update PCI devices tests for core3 API
tests: make tests.extra.VMWrapper hashable
qmemman: do not close stdout/stderr in daemon mode
qmemman: fix early crash
qubesvm: do not try to define libvirt object in offline mode
tests: one more missing virt_mode=hvm
qubesvm: PVH minor improvements
tests: minor fixes
tests: add run_service and qrexec_policy wrappers to ExtraTestCase
tests: clear PCIDevice cache after each test
importing pkg_resources and looking up entry points wastes 100ms+
of time, which is totally unnecessary
This is based on
QubesOS/qubes-core-admin-client@b731ef3885
by @qubesuser
clear_outdated_error_markers crashes if memory stats are not retrieved
yet. In practice it crashes at the very first call during daemon
startup, making the whole qmemman unusable.
This fixes bf4306b815
qmemman: clear "not responding" flags when VM require more memory
QubesOS/qubes-issues#3265
- use capital letters in acronyms in documentation to match upstream
documentation.
- refuse to start a PVH with without kernel set - provide meaningful
error message
Forward-ported from qubes-core-agent-linux:
commit aad6fa6d190d24393e326a4c2ff7ebc3b5921641
Author: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Date: Sat Sep 30 04:56:02 2017 +0200
Hint shellcheck where to look for sourced files, if in repository
This will ease running shellcheck from the repository.
* qubesos/pr/180:
vm/qubesvm: default to PVH unless PCI devices are assigned
vm/qubesvm: expose 'start_time' property over Admin API
vm/qubesvm: revert backup_timestamp to '%s' format
doc: link qvm-device man page for qvm-block, qvm-pci, qvm-usb
* qubesos/pr/179:
qmemman: request VMs balloon down with 16MB safety margin
qmemman: clear "not responding" flags when VM require more memory
qmemman: slightly improve logging
qmemman: reformat code, especially comments
