On Sat, Jan 23, 2021 at 11:12:15AM +0100, Peter Krempa wrote: > On Fri, Jan 22, 2021 at 21:32:05 -0500, Masayoshi Mizuma wrote: > > From: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx> > > > > Introduce locking option for disk source of qemu. > > It may be useful to avoid file lock issues. > > Lock issues usually mean that you are doing something wrong. > > > locking option supports three switches; 'auto', 'on' and 'off'. > > The default behaivor will work if locking option isn't set. > > > > Example of the usage: > > > > <disk type='file' device='disk'> > > <driver name='qemu' type='qcow2' cache='none'/> > > <source file='/tmp/QEMUGuest1.img' locking='off'/> > > <target dev='hda' bus='ide'/> > > <address type='drive' controller='0' bus='0' target='0' unit='0'/> > > </disk> > > > > Signed-off-by: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx> > > --- > > docs/schemas/domaincommon.rng | 9 +++++++++ > > src/conf/domain_conf.c | 8 ++++++++ > > src/conf/storage_source_conf.c | 9 +++++++++ > > src/conf/storage_source_conf.h | 14 ++++++++++++++ > > src/libvirt_private.syms | 1 + > > src/qemu/qemu_block.c | 5 +++++ > > 6 files changed, 46 insertions(+) > > Few quick notes: > > - I'm not entirely persuaded that we should at this at all > - qemu locking works to prevent user mistakes > - you really need to know what to expect if you use images which are > used by multiple VMs > > - you really need to add some form of justification, the current one > definitely is insufficient and thus I'm inclined to NACKing the > concept of enabling setting of the locks completely I agree - we should be providing higher level conceptual logic that indirectly maps into the different locking states. For example we have <readonly/> and <shareable/> elements that influence the type of locks held. A flag to unconditionally disable locking entirely feels like it is just hacking around some undefined problem that should be fixed in a better way. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
