Am 03.02.2011 18:21, schrieb Chunqiang Tang: > Hi Kevin, > > Fast Virtual Disk (FVD) has an automated testing tool (see > http://wiki.qemu.org/Features/FVD/Engineering). For a long time, I knew > that QCOW2 could not pass the automated tests. Today I finally sit down to > look into those bugs. I already submitted multiple patches for different > bugs, but there is one case that I am not certain how to handle. Instead > of creating a potentially broken patch, I though you might be able to > handle it better than me. Bugs showed up when the testing tool injected > aio cancel.
We have discussed this before and yes, aio_cancel is a problem. It is very hard to do this correctly, and so most block drivers just wait for completion instead of actually cancelling anything. Given that a cancel shouldn't happen too often, I think it would be reasonable to take the same approach for qcow2. I don't think adding a lot of complexity for getting this right is justified. Stefan, what do you think? Maybe we could even have a default implementation in generic block code? Kevin
