[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel]xl create PV guest with qcow/qcow2 disk images fail
On Wed, 9 Nov 2011, Chunyan Liu wrote: > In a following email you wrote that without the sleep the device is > "not prepared yet". > What do you mean by that? > The device is present but reading/writing to it returns an error? > > If so, rather than a sleep we need an explicit wait for the device > to be ready. Even trying to read from the device in a loop until it > succeeds would be better than a sleep. At least we would know exactly > what we are doing and why we are doing it. > > > OK, after checking qemu-nbd source code, I think I know where the problem is. > I tried to fork_exec "qemu-nbd -c /dev/nbd0 > disk.img", with this command option, qemu-nbd will call daemon(3) to run in > background and itself should exit immediately, > that's why waitpid can successfully wait the exit of qemu-nbd pid and > fork_exec will return 0. The problem is that I > should not use fork_exec return value to decide if the disk.img is already > connected to nbd device. That's not correct. Good. > This is not great. I would read /proc/partitions instead. > > Thanks, that's a better way to find if a nbd device is free. The whole thing > (find a free nbd device and connect disk.img > to that nbd device) seems better to write a script to do that and in libxl > call that script. Maybe, but I think it makes sense for it to be in libxl and after all reading/writing a file can be done quite well in a library too. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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