Re: [Qemu-devel] [RFC][PATCH 9/9] block: Use bdrv_co_* instead of synchronous versions in coroutines

[Stefan Hajnoczi <stefanha@gmail.com>]

On Fri, Jul 15, 2011 at 06:47:39PM +0200, Kevin Wolf wrote:
> If we're already in a coroutine, there is no reason to use the synchronous
> version of block layer functions when a coroutine one exists. This makes
> bdrv_read/write/flush use bdrv_co_* when used inside a coroutine.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block.c |   43 +++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 43 insertions(+), 0 deletions(-)

I made similar changes to prototype qcow2 coroutines.  They allowed
synchronous code to run unmodified inside a coroutine.

But do we want to keep the synchronous APIs?  They tend to be misused
because they allow synchronous implementation of devices (extboot,
onenand, and others).

The only reason to keep these around is for qemu-img and perhaps some
startup code before the VM is running.  But I think we could tackle
those cases too simply by running in a coroutine and using a common
event loop (which makes timers and bottom halves work too).

Stefan