Am 07.12.2009 15:53, schrieb Anthony Liguori: > Daniel P. Berrange wrote: >> It is safe if you assume that no one else has tried to modify the disk >> since you opened it, otherwise you'd be commiting changes against a >> base state which no longer exists. > > 1) first user opens cow1.qcow, acquires F_WRLCK > 2) first user opens base.qcow, acquires F_RDLCK > 3) second user opens cow2.qcow, acquires F_WRLCK > 4) second user opens base.qcow, acquires F_RDLCK > > 5) second user attempts to commit cow2.qcow to base.qcow
This is broken regardless of locking (except for very... special use that I don't want to even think about, I'd call it criminal). Better don't commit to a backing file that is used by other COW images. Kevin
