Commit Graph

32588 Commits

Author SHA1 Message Date
Peter Krempa
afa15d78cb qemu: hotplug: Use typecasted enum in qemuDomainDetachDeviceDiskLive
Use the correct type in switch and populate the missing cases.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
2019-03-15 16:11:20 +01:00
Peter Krempa
70d0689812 qemu: hotplug: Remove 'ret' variable in qemuDomainDetachDeviceDiskLive
We don't have any cleanup section, we can return the value directly.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
2019-03-15 16:11:20 +01:00
Eric Blake
a6a25d5cb6 snapshot: More clarification about REDEFINE
Based on recent list questions about the proposed addition of
virDomainCheckpointCreateXML(REDEFINE), it is worth adding some
clarification to the existing snapshot redefine documentation that is
serving as the basis for checkpoints.

Normal snapshot creation requires very few elements from the user XML
(libvirt can pick sane defaults for items that are omitted, and many
fields, including <domain>, are documented as readonly output fields
ignored on input, produced by drivers that track it). But during
REDEFINE, the API wants the complete XML produced by an earlier
virDomainSnapshotGetXMLDesc; as the domain definition has likely
changed since the snapshot was first created, libvirt is unable to
recreate a <domain> sub-element that matches the original output
representing the domain state at the time the snapshot was first
created. In fact, reverting without a <domain> sub-element is risky
enough that we had to add a FORCE flag for virDomainSnapshotRevert().
In short, we only support omitting domain for qemu because of
backwards-compatibility to snapshots created before 0.9.5 started
capturing <domain>; even though there are other drivers like vbox that
do not output <domain> because they have other reliable ways to
revert.

And based on the confusion caused when omitting <domain> from snapshot
XML, the initial design for checkpoints in later patches will make
<domain> a mandatory element during its REDEFINE.

[Side note: the fact that <domain> can appear in <domainsnapshot> is a
reason we cannot add a new API for a bulk listing or redefine of all
snapshots of a single domain in one XML call (for example, a 1M
<domain> XML * 16 snapshots explodes into 16M in a bulk form, which
gets difficult to send over RPC). Perhaps we could add a flag to
request that the <domain> sub-element be omitted on output, but such
output is no longer suitable for sane REDEFINE input.]

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
2019-03-15 08:32:37 -05:00
Eric Blake
632ac8f8e7 virobject: Improve documentation
I had to inspect the code to learn whether a final virObjectUnref()
calls ALL dispose callbacks in child-to-parent order (akin to C++
destructors), or whether I manually had to call a parent-class dispose
when writing a child class dispose method.  The answer is the
former. (Thankfully, since VIR_FREE wipes out pointers for safety,
even if I had guessed wrong, I probably would not have tripped over a
double-free fault when the parent dispose ran for the second time).  I
also had to read the code to learn if a dispose method was even
mandatory (it is not, although getting NULL through VIR_CLASS_NEW
requires a macro).  While at it, the VIR_CLASS_NEW macro requires that
the virObject component at offset 0 be reached through the name
'parent', not 'object'.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Erik Skultety <eskultet@redhat.com>
2019-03-15 08:30:47 -05:00
Michal Privoznik
c2bc419131 qemu_hotplug: Fix a rare race condition when detaching a device twice
https://bugzilla.redhat.com/show_bug.cgi?id=1623389

If a device is detached twice from the same domain the following
race condition may happen:

1) The first DetachDevice() call will issue "device_del" on qemu
monitor, but since the DEVICE_DELETED event did not arrive in
time, the API ends claiming "Device detach request sent
successfully".

2) The second DetachDevice() therefore still find the device in
the domain and thus proceeds to detaching it again. It calls
EnterMonitor() and qemuMonitorSend() trying to issue "device_del"
command again. This gets both domain lock and monitor lock
released.

3) At this point, qemu sends us the DEVICE_DELETED event which is
going to be handled by the event loop which ends up calling
qemuDomainSignalDeviceRemoval() to determine who is going to
remove the device from domain definition. Whether it is the
caller that marked the device for removal or whether it is going
to be the event processing thread.

4) Because the device was marked for removal,
qemuDomainSignalDeviceRemoval() returns true, which means the
event is to be processed by the thread that has marked the device
for removal (and is currently still trying to issue "device_del"
command)

5) The thread finally issues the "device_del" command, which
fails (obviously) and therefore it calls
qemuDomainResetDeviceRemoval() to reset the device marking and
quits immediately after, NOT removing any device from the domain
definition.

At this point, the device is still present in the domain
definition but doesn't exist in qemu anymore. Worse, there is no
way to remove it from the domain definition.

Solution is to note down that we've seen the event and if the
second "device_del" fails, not take it as a failure but carry on
with the usual execution.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
ACKed-by: Peter Krempa <pkrempa@redhat.com>
2019-03-15 13:45:34 +01:00
Michal Privoznik
229a0358f0 qemuMonitorJSONDelDevice: Return -2 on DeviceNotFound error
A caller might be interested in differentiating the cause for
error, especially if DeviceNotFound error occurred.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
ACKed-by: Peter Krempa <pkrempa@redhat.com>
2019-03-15 13:45:34 +01:00
Michal Privoznik
4cd13478ac qemu_hotplug: Introduce and use qemuDomainDeleteDevice
The aim of this function will be to fix return value of
qemuMonitorDelDevice() in one specific case. But that is yet to
come. Right now this is nothing but a plain substitution.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
ACKed-by: Peter Krempa <pkrempa@redhat.com>
2019-03-15 13:45:34 +01:00
Andrea Bolognani
641438fb75 run: Don't export unnecessary paths
We're using virFileFindResourceFull() to locate resources
nowadays, which makes exporting these information in the
environment unnecessary: see

  virDriverLoadModule() for LIBVIRT_DRIVER_DIR
  virLockManagerPluginNew() for LIBVIRT_LOCK_MANAGER_PLUGIN_DIR
  virLockManagerLockDaemonConnectionNew() for VIRTLOCKD_PATH
  doRemoteOpen() for LIBVIRTD_PATH

As further proof that we don't need to expose the information
this way anymore, we're not even exporting VIRTLOGD_PATH, which
would be necessary if virLogManagerConnect() didn't already
take care of that for us.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
2019-03-15 11:50:23 +01:00
Jiri Denemark
1c2a9260e8 qemu: Set job statsType for external memory snapshot
Any job which is able to provide statistics that can be queried via
virDomainGetJob{Stats,Info} has to set an appropriate statsType.

Without a proper statsType qemuDomainJobInfoToParams and
qemuDomainJobInfoToInfo have no idea what statistics should be sent to
the API caller.

https://bugzilla.redhat.com/show_bug.cgi?id=1688774

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Erik Skultety <eskultet@redhat.com>
2019-03-15 09:39:19 +01:00
Cole Robinson
4ec884e387 test: storage: Fill in default vol types for every pool
Fill in a default volume type for every pool type, as reported
by the VolGetInfo API. Now that we cover the whole enum, report
an error for invalid values.

Reviewed-by: Andrea Bolognani <abologna@redhat.com>
Signed-off-by: Cole Robinson <crobinso@redhat.com>
2019-03-14 20:53:46 -04:00
Cole Robinson
47cbc92987 docs: hacking: Add 'Code coverage reports' section
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
Signed-off-by: Cole Robinson <crobinso@redhat.com>
2019-03-14 20:47:15 -04:00
Cole Robinson
f38d553e2d configure: Remove --enable-test-coverage
We provide a custom configure option --enable-test-coverage and
'make cov' target to generate code coverage reports. However gnulib
already provides a 'make coverage' which 'just works' and doesn't
require a special configure option.

This drops our custom implementation in favor of 'make coverage'.
Reports are now output to cov/index.html

Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
Signed-off-by: Cole Robinson <crobinso@redhat.com>
2019-03-14 20:47:15 -04:00
Michal Privoznik
2a00ef6e71 virt-driver-qemu.m4: Require YAJL
There is no way that qemu driver can work without being able to
format/parse JSON.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
2019-03-14 17:27:56 +01:00
Michal Privoznik
5f2adfab59 virt-driver-qemu.m4: Make qemu driver optional
The basic idea of our configure script is to probe for things
rather than have them enabled by default. This is even more
visible in the next commit where configure fails if qemu driver
is enabled but no yajl is found.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>
2019-03-14 17:27:49 +01:00
Michal Privoznik
0b3f7ec884 virt-yajl.m4: Drop useless check for qemu
The code tries to detect installed version of qemu to learn if it
uses HMP or QMP and enable YAJL based on that. Well, we support
only QMP and also minimal required version of qemu is 1.5.0 so
the check would have enabled yajl anyway.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
2019-03-14 14:29:48 +01:00
Eric Blake
3ad7c2e610 news: Document recent snapshot topological flag
A new API flag is news-worthy.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
2019-03-14 07:46:43 -05:00
Suyang Chen
265e6924f5 conf: Introduce virDomainDefCputuneValidate helper
Introduce a simple validation helper to perform the cputune period and
quota checks so that we can get rid of those repetitive chunks. Since
this is a validation helper, this patch also moves the checks from the
'parse' phase into the 'validation' phase.

Signed-off-by: Suyang Chen <dawson0xff@gmail.com>
Reviewed-by: Erik Skultety <eskultet@redhat.com>
2019-03-14 10:44:44 +01:00
Andrea Bolognani
ca1471622d Don't define abs_* variables ourselves
Apparently this was necessary in the past because old versions
of autoconf/automake didn't make them available, but these
days all of the platforms we target include recent enough
autotools - as evidenced by the fact that, for example, we
already use abs_top_srcdir in tools/ despite the fact that
tools/Makefile.am is missing the same boilerplate.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
2019-03-14 10:05:32 +01:00
Andrea Bolognani
349d49637c tests: Don't redefine variables for TESTS_ENVIRONMENT
We already have code that defines all abs_* variables at the
top of tests/Makefile.am, so there is no point in redefining
them a second time (using a slightly different shell
incantation to boot).

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
2019-03-14 10:05:30 +01:00
Andrea Bolognani
c0a4a98eab Fix names for abs_top_{src,build}dir variables
According to the official documentation for autoconf[1], the
correct names for these variables are abs_top_{src,build}dir
rather than abs_top{src,build}dir; in fact, we're already
using the correct names in various places, so let's just make
everything nice and consistent.

[1] https://www.gnu.org/software/autoconf/manual/autoconf-2.69/html_node/Preset-Output-Variables.html

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
2019-03-14 10:05:28 +01:00
Andrea Bolognani
cd01258714 tests: Stop looking for abs_top_srcdir in the environment
This code snippet has clearly been cargo-culted, and all its
instances can be safely dropped seeing as 1) a much better
way to handle the scenario in C programs would be to pass the
value via the preprocessor, and 2) the value is actually not
used anywhere after being defined.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
2019-03-14 10:05:25 +01:00
Andrea Bolognani
625c78b5c1 tests: Don't define TEST_DRIVER_DIR
It's no longer used anywhere.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
2019-03-14 10:05:23 +01:00
Andrea Bolognani
3e8c2f30b1 tests: Don't use TEST_DRIVER_DIR in virTestCaptureProgramExecChild()
TEST_DRIVER_DIR is defined as "$(top_builddir)/src/.libs"; however,
as of commit bc6e206322, virDriverLoadModule() will search (the
absolute version of) that directory automatically, which means
passing it through the environment is no longer necessary.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
2019-03-14 10:05:21 +01:00
Andrea Bolognani
b635eb8575 tests: Drop LIBVIRT_DRIVER_DIR from TESTS_ENVIRONMENT
LIBVIRT_DRIVER_DIR is defined as (what is for all intents and
purposes equivalent to) "$(abs_top_builddir)/src/.libs"; however,
as of commit bc6e206322, virDriverLoadModule() will search that
directory automatically, which means passing it through the
environment is no longer necessary.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
2019-03-14 10:05:19 +01:00
Andrea Bolognani
d24bb02b8c tests: Drop CONFIG_HEADER from TESTS_ENVIRONMENT
It's no longer used as of commit a9694a8e18.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
2019-03-14 10:05:13 +01:00
Eric Blake
4332c4d345 qemu: clean up qemuDomainRemoveInactiveCommon
Use VIR_AUTOFREE and saner formatting. No semantic change.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: John Ferlan <jferlan@redhat.com>
2019-03-13 20:29:48 -05:00
Eric Blake
94bbe3da4f domain_conf: Expose virDomainStorageNetworkParseHost
An upcoming patch wants to reuse XML parsing of both unix and tcp
network host descriptions in the context of setting up a backup
NBD server. Make that easier by refactoring the existing parser.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: John Ferlan <jferlan@redhat.com>
2019-03-13 20:28:57 -05:00
Eric Blake
9d458bd913 docs: Consistent spacing in *GetXMLDesc functions
We copy-and-paste a lot of our docs, as evidenced by the number of
*GetXMLDesc() functions which had the same unusual indentation and
missing capital in the second sentence of the returns paragraph.

Signed-off-by: Eric Blake <eblake@redhat.com>
2019-03-13 20:28:52 -05:00
Eric Blake
f2cb0c8934 vbox: Fix build after xenbus addition
Commit 09eb1ae0 added a new enum type for xenbus, and adjusted
affected switch statements in the qemu driver, but failed to notice
that the vbox driver had a similar switch statement.

Signed-off-by: Eric Blake <eblake@redhat.com>
2019-03-13 20:28:35 -05:00
Jim Fehlig
5a64c202cc xenconfig: Add support for max_grant_frames
Add support in the domXML<->native config converter for
max_grant_frames. Include a test for the conversion.

Signed-off-by: Jim Fehlig <jfehlig@suse.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
2019-03-13 12:06:52 -06:00
Jim Fehlig
ec5a11910d libxl: Add support for max_grant_frames
Add support for setting max_grant_frames in libxl domain config
object and include a test to check that it is properly converted
from XML to libxl domain config.

Signed-off-by: Jim Fehlig <jfehlig@suse.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
2019-03-13 12:06:52 -06:00
Jim Fehlig
fb0597574d libxl: Add implicit xenbus controller
All Xen domains have a xenbus device. Implicitly add one if not
already explicitly specified in the domain config.

Signed-off-by: Jim Fehlig <jfehlig@suse.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
2019-03-13 12:06:52 -06:00
Jim Fehlig
09eb1ae0ec conf: Add a new 'xenbus' controller type
xenbus is virtual controller (akin to virtio controllers) for Xen
paravirtual devices. Although all Xen VMs have a xenbus, it has
never been modeled in libvirt, or in Xen native VM config format
for that matter.

Recently there have been requests to support Xen's max_grant_frames
setting in libvirt. max_grant_frames is best modeled as an attribute
of xenbus. It describes the maximum IO buffer space (or DMA space)
available in xenbus for use by connected paravirtual devices. This
patch introduces a new xenbus controller type that includes a
maxGrantFrames attribute.

Signed-off-by: Jim Fehlig <jfehlig@suse.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
2019-03-13 12:06:52 -06:00
Jim Fehlig
411cdaf884 apparmor: Check libvirtd profile status by name
Commit a3ab6d42 changed the libvirtd profile to a named profile,
breaking the apparmor driver's ability to detect if the profile is
active. When the apparmor driver loads it checks the status of the
libvirtd profile using the full binary path, which fails since the
profile is now referenced by name. If the apparmor driver is
explicitly requested in /etc/libvirt/qemu.conf, then libvirtd fails
to load too.

Instead of only checking the profile status by full binary path,
also check by profile name. The full path check is retained in case
users have a customized libvirtd profile with full path.

Signed-off-by: Jim Fehlig <jfehlig@suse.com>
Acked-by: Jamie Strandboge <jamie@canonical.com>
2019-03-13 11:58:11 -06:00
Shotaro Gotanda
612c0d4bb8 util: Introduce virStringParseYesNo helper
This helper performs a conversion from a "yes|no" string to a
corresponding boolean. This allows us to drop several repetitive
if-then-else string->bool conversion blocks.

Signed-off-by: Shotaro Gotanda <g.sho1500@gmail.com>
Reviewed-by: Erik Skultety <eskultet@redhat.com>
2019-03-13 14:24:18 +01:00
Michal Privoznik
ff86e79faf tests: Call virFileWrapperClearPrefixes() for tests using virFileWrapper
This is mostly to avoid a memleak that is not a true memleak
anyway - prefixes will be freed by kernel upon test exit.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
Reviewed-by: Erik Skultety <eskultet@redhat.com>
2019-03-13 14:16:46 +01:00
Michal Privoznik
6e31c4b27e virFileWrapper: Use VIR_AUTOFREE()
This enables us to simplify the code a bit.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Erik Skultety <eskultet@redhat.com>
2019-03-13 14:16:27 +01:00
Michal Privoznik
288e0ab106 tests: Turn virFileWrapperAddPrefix to void
In theory, it's nice to have virFileWrapperAddPrefix() return a
value that indicates if the function succeeded or not. But in
practice, nobody checks for that and in fact blindly believes
that the function succeeded. Therefore, make the function return
nothing and just abort() if it would fail.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
Reviewed-by: Erik Skultety <eskultet@redhat.com>
2019-03-13 14:15:35 +01:00
Michal Privoznik
8b71b0c727 qemu_hotplug: Properly check for qemuMonitorDelDevice retval
Luckily, the function returns only 0 or -1 so all the checks work
as expected. Anyway, our rule is that a positive value means
success so if the function ever returns a positive value these
checks will fail. Make them check for a negative value properly.

At the same time fix qemuDomainDetachExtensionDevice() reval
check. It is somewhat related to the aim of this patch.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
2019-03-13 14:09:09 +01:00
Michal Privoznik
1dd24167b8 news: Document firmware autoselection for QEMU driver
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Erik Skultety <eskultet@redhat.com>
2019-03-13 13:11:25 +01:00
Michal Privoznik
6d9542e340 qemuFirmwareFetchConfigs: Fix check for @privileged
The qemuFirmwareFetchConfigs() function is supposed to fetch all
firmware descriptions from paths defined by firmware.json
specification. This includes user's $HOME directory. However, it
was agreed that if libvirtd is running as privileged user then
his $HOME is ignored (thus $HOME is included in the search only
for regular users). Well, I got the condition wrong - it should
have been reversed.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Andrea Bolognani <abologna@redhat.com>
2019-03-13 13:11:25 +01:00
Andrea Bolognani
60943f0eec tests: Use testQemuCapsIterate()
With only a couple minor tweaks, we can make the existing
doCapsTest() functions with testQemuCapsIterate() and finally
remove the need to manually adjust the test programs every time
a new input file is introduced; moreover, this means that the
two lists can't possibly get out of sync anymore.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Acked-by: Peter Krempa <pkrempa@redhat.com>
2019-03-13 11:07:12 +01:00
Andrea Bolognani
30439c1b81 tests: Introduce testQemuCapsIterate()
This function iterates over a directory containing
capabilities-related data, extract some useful bits of
information from the file name, and calls a user-provided
callback.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Acked-by: Peter Krempa <pkrempa@redhat.com>
2019-03-13 11:07:10 +01:00
Andrea Bolognani
6000bd1342 tests: Add testutilsqemu dependency for qemucaps2xmltest
We're not using any of the functionality offered by the
module at the moment, but we will in just a second.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Acked-by: Peter Krempa <pkrempa@redhat.com>
2019-03-13 11:07:07 +01:00
Andrea Bolognani
ad340f225a tests: Move code from DO_TEST() to doCapsTest()
This removes the awkard escaping and will allow us to perform
some more refactoring later on.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Acked-by: Peter Krempa <pkrempa@redhat.com>
2019-03-13 11:07:06 +01:00
Andrea Bolognani
5a8ceba2f3 tests: Use virAsprintf() to build titles
We're using static string concatenation at the moment, but
that will no longer be a possibility in a bit.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Acked-by: Peter Krempa <pkrempa@redhat.com>
2019-03-13 11:07:04 +01:00
Andrea Bolognani
0c744afe1a tests: Move data directories into testQemuData
This removes a little duplication right away, and will allow
us to avoid introducing more later on.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Acked-by: Peter Krempa <pkrempa@redhat.com>
2019-03-13 11:07:03 +01:00
Andrea Bolognani
c125a6ef2a tests: Move ret into testQemuData
This is not particularly useful right now, but will allow us
to refactor some functionality later on.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Acked-by: Peter Krempa <pkrempa@redhat.com>
2019-03-13 11:07:01 +01:00
Andrea Bolognani
31044d6ff2 tests: Introduce testQemuDataInit() and testQemuDataReset()
These functions don't do anything too interesting right now,
but will be extended later on.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Acked-by: Peter Krempa <pkrempa@redhat.com>
2019-03-13 11:06:56 +01:00
Eric Blake
c615c14246 virsh: Add snapshot-list --topological
For snapshots, virsh already has a (shockingly naive [1]) client-side
topological sorter with the --tree option. But as a series of REDEFINE
calls must be presented in topological order, it's worth letting the
server do the work for us, especially since the server can give us a
topological sorting with less effort than our naive client
reconstruction.

[1] The XXX comment in virshSnapshotListCollect() about --tree being
O(n^3) is telling; https://en.wikipedia.org/wiki/Topological_sorting
is an interesting resource describing Kahn's algorithm and other
approaches for O(n) topological sorting for anyone motivated to use a
more elegant algorithm than brute force - but that doesn't affect this
patch.

For now, I am purposefully NOT implementing virsh fallback code to
provide a topological sort when the flag was rejected as unsupported;
we can worry about that down the road if users actually demonstrate
that they use new virsh but old libvirt to even need the fallback.
(The code we use for --tree could be repurposed to be such a fallback,
whether or not we keep it naive or improve it to be faster - but
again, no one should spend time on a fallback without evidence that we
need it.)

The test driver makes it easy to test:
$ virsh -c test:///default '
snapshot-create-as test a
snapshot-create-as test c
snapshot-create-as test b
snapshot-list test
snapshot-list test --topological
snapshot-list test --descendants a
snapshot-list test --descendants a --topological
snapshot-list test --tree
snapshot-list test --tree --topological
'

Without any flags, virsh does client-side sorting alphabetically, and
lists 'b' before 'c' (even though 'c' is the parent of 'b'); with the
flag, virsh skips sorting, and you can now see that the server handed
back data in a correct ordering. As shown here with a simple linear
chain, there isn't any other possible ordering, so --tree mode doesn't
seem to care whether --topological is used.  But it is possible to
compose more complicated DAGs with multiple children to a parent
(representing reverting back to a snapshot then creating more
snapshots along those divergent execution timelines), where it is then
possible (but not guaranteed) that adding the --topological flag
changes the --tree output (the client-side --tree algorithm breaks
ties based on alphabetical sorting between two nodes that share the
same parent, while the --topological sort skips the client-side
alphabetical sort and ends up exposing the server's internal order for
siblings, whether that be historical creation order or dependent on a
random hash seed).  But even if the results differ, they will still be
topologically correct.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
2019-03-12 20:46:09 -05:00