Am 28.05.2013 um 11:24 hat Paolo Bonzini geschrieben: > Il 28/05/2013 11:18, Kevin Wolf ha scritto: > >>> The other part why I haven't sent a fix yet is that I don't have a test > >>> case for it. > >> > >> Temporarily add a sleep(31) in qemu_fdatasync()? > >> > >> I was lazy in testing with -snapshot to not corrupt my disk image, which > >> would not trigger the same issue since qcow2-backed AFAIU. > >> > >>> I guess I need to extend blkdebug first before this can be > >>> reliably tested by qtest. > >> > >> It can't, since it's not a pure device emulation issue but depends on > >> the relative timing of filesystem operations and subsequent commands. > > > > That's why you need to take influence on the timing. It's no excuse for > > merging without a test case. If we only ever tested devices that have no > > relation to the outside world, our testing would be pretty useless and > > always stay as bad as it is today in many areas. > > I don't think the qtest would be timing dependent. The Linux testcase > is timing dependent, but for the qtest all you need to check is "is BUSY > set during a flush?". This can be done with blkdebug suspend/resume, > except that there is no way to call bdrv_debug_resume from QEMU.
That's exactly what I was talking about, suspending a request is taking influence on its timing. I'm looking into this right now. (And it's not just resume, bdrv_debug_suspend can't be called from QEMU either) In fact, I'm checking whether we can have a monitor command to issue qemu-io commands, which will be more generally useful for test cases. We just need to make obvious that it doesn't become an ABI. Maybe prefix it with "__org.qemu.debug-" or something like that. Kevin
