On Wed, Jul 1, 2015 at 4:52 PM, Markus Armbruster <arm...@redhat.com> wrote: > Stefan Hajnoczi <stefa...@redhat.com> writes: > >> On Mon, Jun 29, 2015 at 08:10:20AM +0200, Markus Armbruster wrote: >>> Alexander Yarygin <yary...@linux.vnet.ibm.com> writes: >>> > Markus Armbruster <arm...@redhat.com> writes: >>> > * Ignorant answer: I was told that the bdrv_drain_all()'s comment is >>> > obsolete and we can use bdrv_drain(). Here is a link to the old >>> > thread: http://marc.info/?l=qemu-devel&m=143154211017926&w=2. >>> >>> Kevin, Stefan, if the comment has become wrong, it needs to be redone. >>> Who's going to take care of it? >> >> I couldn't think of a scenario where this patch is unsafe. >> >> The danger is that the I/O code path depends on something outside the >> AioContext. In that case you block in aio_poll(aio_context, true) >> forever without making progress. The thing the I/O request depends on >> will never finish. >> >> Code that accesses multiple BDSes puts them into the same AioContext, so >> this should not be a problem in practice. > > Stefan, could you rework the bdrv_drain()'s to spell out how it can be > used safely?
Good idea. I will send a patch.
