Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks.

[Anthony Liguori]

Daniel P. Berrange wrote:
> That doesn't work in the case of setting up a clustered filesystem
> shared between guests. That requires that the disk be opened writable,
> but with a shared (F_RDLOCK) lock.
>   

If you'd like data corruption :-)

qemu -drive file=/dev/hda,lock=shared   # clustered file system
qemu -drive file=/dev/hda,lock=shared   # clustered file system

qemu -drive file=/dev/hda,lock=shared -snapshot  # i have no awareness 
of the last two.

The 3rd invocation is totally fine.  /dev/hda is shared (but the 
expectation is read-only).

Better to stick with on/off.  That gives much easier to understand 
semantics.

Regards,

Anthony Liguori