On 12/05/2009 12:29 AM, Anthony Liguori wrote:
Well disk sharing isn't actually bad as long as it's raw or a physical
device.
For qcow2, it's very complicated by backing files because we really
need to express the concept of a read-write lock.
That is, as long as the guests are opening the file read only, you
should allow many readers. However, you should prevent anyone from
opening with write permission. Likewise, writes should prevent future
reads.
Well shared/exclusive or read/write locks support exactly that.
For non-raw storage we should take the locks unconditionally, since
there is no useful way to share such images opened for write access.
--
Do not meddle in the internals of kernels, for they are subtle and quick to
panic.
