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Michal Privoznik 379c0ce4bf qemu_namespace: Umount the original /dev before replacing it with tmpfs
Our code relies on mount events propagating into the namespace we
create for a domain. However, there's one caveat. In v8.8.0-rc1~8
I've tried to make us detect differences in mount tables between
the namespace in which libvirtd runs and the domain namespace.
This is crucial for any mounts that happen after the domain was
started (for instance new hugetlbfs can be mounted on say
/dev/hugepages1G).

Therefore, we take a look into /proc/$(pgrep qemu)/mounts to see
what filesystems are mounted under /dev. Now, since we don't
umount the original /dev, just mount a tmpfs over it, we get all
the events (e.g. aforementioned hugetlbfs mount on
/dev/hugepages1G), but we are not really able to access it
because of the tmpfs that's placed on top. This then confuses our
algorithm for detecting which filesystems are mounted (the
algorithm is implemented in qemuDomainGetPreservedMounts()).

To break the link between host's and guest's /dev we just need to
umount() the original /dev in the namespace. Just before our
artificially created tmpfs is moved into its place.

Fixes: 46b03819ae8d833b11c2aaccb2c2a0361727f51b
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2151869#c6
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
2023-01-05 12:57:49 +01:00
2019-05-31 17:54:28 +02:00
2023-01-03 13:44:15 +01:00
2019-09-06 12:47:46 +02:00
2022-03-17 14:33:12 +01:00
2020-01-16 13:04:11 +00:00
2020-08-03 09:26:48 +02:00
2019-10-18 17:32:52 +02:00
2015-06-16 13:46:20 +02:00
2022-12-14 19:24:01 +01:00
2020-08-03 15:08:28 +02:00

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==============================
Libvirt API for virtualization
==============================

Libvirt provides a portable, long term stable C API for managing the
virtualization technologies provided by many operating systems. It
includes support for QEMU, KVM, Xen, LXC, bhyve, Virtuozzo, VMware
vCenter and ESX, VMware Desktop, Hyper-V, VirtualBox and the POWER
Hypervisor.

For some of these hypervisors, it provides a stateful management
daemon which runs on the virtualization host allowing access to the
API both by non-privileged local users and remote users.

Layered packages provide bindings of the libvirt C API into other
languages including Python, Perl, PHP, Go, Java, OCaml, as well as
mappings into object systems such as GObject, CIM and SNMP.

Further information about the libvirt project can be found on the
website:

https://libvirt.org


License
=======

The libvirt C API is distributed under the terms of GNU Lesser General
Public License, version 2.1 (or later). Some parts of the code that are
not part of the C library may have the more restrictive GNU General
Public License, version 2.0 (or later). See the files ``COPYING.LESSER``
and ``COPYING`` for full license terms & conditions.


Installation
============

Instructions on building and installing libvirt can be found on the website:

https://libvirt.org/compiling.html

Contributing
============

The libvirt project welcomes contributions in many ways. For most components
the best way to contribute is to send patches to the primary development
mailing list. Further guidance on this can be found on the website:

https://libvirt.org/contribute.html


Contact
=======

The libvirt project has two primary mailing lists:

* libvirt-users@redhat.com (**for user discussions**)
* libvir-list@redhat.com (**for development only**)

Further details on contacting the project are available on the website:

https://libvirt.org/contact.html
Description
Libvirt native C API and daemons
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