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June 2026

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[PATCHv2] lxc: truncate LOOP_GET_STATUS64.lo_file_name for long loop backing paths
by Radoslaw Smigielski 01 Jun '26

01 Jun '26

From: Radoslaw Smigielski <rsmigiel(a)redhat.com> LXC domains using a file-backed filesystem with the loop driver fail to start when the backing image path is longer than LO_NAME_SIZE (64 bytes, 63 characters plus NUL). virFileLoopDeviceAssociate() treated a failed virStrcpy() into loop_info64.lo_file_name as fatal and reported a misleading virReportSystemError(errno, ...), so users saw errors such as "Unable to set backing file ...: Success" or ENOENT even when the file existed. The kernel only stores a short name in lo_file_name for LOOP_SET_STATUS64 metadata. The backing file is opened by full path. Copy the path with virStrcpy(), allow truncation into lo_file_name, and mark truncation with '*' at LO_NAME_SIZE - 2 to match losetup behavior. Log truncation at debug level only. XML example that failed before this change: <filesystem type='file' accessmode='passthrough'> <driver type='loop' format='raw'/> <source file='/root/demoaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa.raw'/> <target dir='/'/> </filesystem> Fixes: https://gitlab.com/libvirt/libvirt/-/work_items/63 Signed-off-by: Radoslaw Smigielski <rsmigiel(a)redhat.com> --- src/util/virfile.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/src/util/virfile.c b/src/util/virfile.c index a0c6cb804862..443d0ed9adab 100644 --- a/src/util/virfile.c +++ b/src/util/virfile.c @@ -995,11 +995,15 @@ int virFileLoopDeviceAssociate(const char *file, lo.lo_flags = LO_FLAGS_AUTOCLEAR; - /* Set backing file name for LOOP_GET_STATUS64 queries */ + /* lo_file_name is loop device name, max length is LO_NAME_SIZE bytes. + * Truncate loop device name if file path is longer than LO_NAME_SIZE, + * and still use the full path to open backing file. */ if (virStrcpy((char *) lo.lo_file_name, file, LO_NAME_SIZE) < 0) { - virReportSystemError(errno, - _("Unable to set backing file %1$s"), file); - goto cleanup; + /* virStrcpy() only returns -1 on truncation. Mark truncation with + * asterisk at position LO_NAME_SIZE-2 to match losetup behavior. */ + lo.lo_file_name[LO_NAME_SIZE - 2] = '*'; + VIR_DEBUG("lo_file_name for '%s' truncated to %d bytes in loop metadata", + file, LO_NAME_SIZE); } if ((fsfd = open(file, O_RDWR)) < 0) { -- 2.54.0

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Release of libvirt-12.4.0
by Jiri Denemark 01 Jun '26

01 Jun '26

The 12.4.0 release of both libvirt and libvirt-python is tagged and signed tarballs are available at https://download.libvirt.org/ https://download.libvirt.org/python/ Thanks everybody who helped with this release by sending patches, reviewing, testing, or providing feedback. Your work is greatly appreciated. * Removed features * qemu: Bump minimum version to QEMU-7.2 The minimal required version of QEMU was bumped to 7.2.0. * New features * resctrl: Add energy monitoring via resctrl's PERF_PKG_MON Add support for Linux kernel 7.0 feature - energy monitoring via resctrl. This allows to monitor per-VM energy consumption on supported platforms. Implemented via ``energytune`` element in ``cputune`` . * Add channel lifecycle domain event Add support for a new domain event which can be used to track the state of any virtio channel. It is similar to guest agent lifecycle event. * bhyve: Add memory tuning support The bhyve driver now allows setting a domain's memory hard limit using the following syntax:: <memtune> <hard_limit unit='G'>1</hard_limit> </memtune> It also implements the ``virDomainGetMemoryParameters()`` and ``virDomainSetMemoryParameters()`` APIs for controlling the memory hard limit of a running domain. * bhyve: Add virtio-console device support Domain XML can now use ``virtio-console`` devices. Among other things, these devices can be used to configure a QEMU Guest Agent:: <devices> <channel type='unix'> <source mode='bind' path='/var/run/libvirt/bhyve/bhyve.agent'/> <target type='virtio' name='org.qemu.guest_agent.0'/> <address type='virtio-serial' controller='0' bus='0' port='1'/> </channel> </devices> Additionally, the ``virDomainQemuAgentCommand()`` API which allows running arbitrary guest agent commands is now supported. The ``virDomainGetHostname()`` API, used to query the hostname of a guest, now supports using the guest agent as a source of information. * Improvements * vircgroupv2: Implement freezer controller The CGroupV2 code now supports freezer controller which allows suspending and resuming of LXC domains. * virnetdevbandwidth: Only clear qdisc for defined directions Setting a QoS on a vNIC no longer leads to clearing (preconfigured) root queuing discipline ('qdisc`) in both directions (egress, ingress), only the affected one. * Bug fixes * storage: ZFS: Fix incorrect volsize and refreservation on zvol creation When creating a zvol, the ZFS driver listed all volumes in the pool and updated the new volume's size with data from the last volume in the list rather than the matching one. Now it correctly returns on valid one. * esx/vmware: VMs are tracked under different UUIDs by default The VMWare-related drivers were using allegedly unique IDs for domains, but it turned out they were not completely unique, even for the same host. That caused an issue where a different domain could have been acted upon then requested. Unfortunately, to make this work, the UUIDs of all VMWare-related domains will change from this release. In order to use the pre-v12.4.0 behaviour there is a new URI query parameter ``legacy_uuid`` which, if set to ``1``, will revert to the older way of working. * virsh: Provide no auth callbacks for bash completer The bash completer script calls virsh to provide completions. In some cases the underlying virsh might get stuck waiting on input (e.g. password for SSH session). Not anymore. * virauth: Verify virConnectAuth::cb is set in virAuthGetPasswordPath() A check was missing in ``virAuthGetPasswordPath()`` which might lead to crash of the client library when NULL callback was provided. This is now fixed. Enjoy. Jirka

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