633b699bfd
The iohelper currently calls saferead() to get data from the underlying file. This has a problem with O_DIRECT when hitting end-of-file. saferead() is asked to read 1MB, but the first read() it does may return only a few KB, so it'll try another read() to fill the remaining buffer. Unfortunately the buffer pointer passed into this 2nd read() is likely not aligned to the extent that O_DIRECT requires, so rather than seeing '0' for end-of-file, we'll get -1 + EINVAL due to misaligned buffer. The way the iohelper is currently written, it already handles getting short reads, so there is actually no need to use saferead() at all. We can simply call read() directly. The benefit of this is that we can now write() the data immediately so when we go into the subsequent reads() we'll always have a correctly aligned buffer. Technically the file position ought to be aligned for O_DIRECT too, but this does not appear to matter when at end-of-file. Tested-by: Nikolay Shirokovskiy <nshirokovskiy@virtuozzo.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
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:
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 2.1 (or later). See the files COPYING.LESSER
and COPYING for full license terms & conditions.
Installation
Libvirt uses the GNU Autotools build system, so in general can be built and installed with the usual commands. For example, to build in a manner that is suitable for installing as root, use:
$ ./configure --prefix=/usr --sysconfdir=/etc --localstatedir=/var
$ make
$ sudo make install
While to build & install as an unprivileged user
$ ./configure --prefix=$HOME/usr
$ make
$ make install
The libvirt code relies on a large number of 3rd party libraries. These will
be detected during execution of the configure script and a summary printed
which lists any missing (optional) dependencies.
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: