On 08/20/2015 01:14 AM, Peter Lieven wrote: > the blk_drain_all() that is executed if the guest issues a DMA cancel > leads to a stuck main loop if the storage backend (e.g. a NFS share) > is unresponsive. > > This scenario is a common case for CDROM images mounted from an > NFS share. In this case a broken NFS server can take down the > whole VM even if the mounted CDROM is not used and was just not > unmounted after usage. > > This approach avoids the blk_drain_all for read-only media and > cancelles the AIO locally and makes the callback a NOP if the
s/cancelles/cancels/
> original request is completed after the NFS share is responsive
> again.
>
> Signed-off-by: Peter Lieven <p...@kamp.de>
> ---
> hw/ide/pci.c | 32 ++++++++++++++++++--------------
> 1 file changed, 18 insertions(+), 14 deletions(-)
> + if (!bdrv_is_read_only(bm->bus->dma->aiocb->bs)) {
> + /* We can't cancel Scatter Gather DMA in the middle of
> the
> + * operation or a partial (not full) DMA transfer would
> + * reach the storage so we wait for completion instead
> + * (we beahve like if the DMA was completed by the time
> the
s/beahve like/behave as/
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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