Re: [libvirt] [Qemu-devel] [PATCH v2 3/3] raw-posix: Re-open host CD-ROM after media change

On Mon, Apr 4, 2011 at 2:49 PM, Avi Kivity <avi(a)redhat.com&gt; wrote: > On 04/04/2011 04:38 PM, Anthony Liguori wrote: >> >> On 04/04/2011 08:22 AM, Avi Kivity wrote: >>> >>> On 04/03/2011 02:57 PM, Stefan Hajnoczi wrote: >>>> >>>> In order for media change to work with Linux host CD-ROM it is >>>> necessary to reopen the file (otherwise the inode size will not >>>> refresh, this is an issue with existing kernels). >>>> >>> >>> Maybe we should fix the bug in Linux (and backport as necessary)? >>> >>> I think cd-rom assignment is sufficiently obscure that we can require a >>> fixed kernel instead of providing a workaround. >> >> Do reads fail after CD change?  Or do they succeed and the size is just >> reported incorrectly? >> >> If it's the later, I'd agree that it needs fixing in the kernel.  If it's >> the former, I'd say it's clearly a feature. >> > > Even if it's a documented or intentional feature, we can add an ioctl to > "refresh" the device with up-to-date data. It's possible to fix this in the kernel. I just haven't written the patch yet. The inode size needs to be updated when the new medium is detected. I haven't tested but I suspect reads within the size of the previous medium will succeed. But if the new medium is larger then reads beyond the old medium size will fail.