Re: [Qemu-devel] [PATCH 17/18] qemu-io: Add background write

[Fam Zheng]

On Mon, 09/18 19:53, Max Reitz wrote:
> On 2017-09-18 08:46, Fam Zheng wrote:
> > On Wed, 09/13 20:19, Max Reitz wrote:
> >> Add a new parameter -B to qemu-io's write command.  When used, qemu-io
> >> will not wait for the result of the operation and instead execute it in
> >> the background.
> > 
> > Cannot aio_write be used for this purpose?
> 
> Depends.  I have been trained to dislike *_aio_*, so that's probably the
> initial reason why I didn't use it.
> 
> Second, I'd have to fix aio_write before it can be used.  Currently,
> this aborts:
> 
> echo 'qemu-io drv0 "aio_write -P 0x11 0 64M"' \
>     | x86_64-softmmu/qemu-system-x86_64 -monitor stdio \
>           -blockdev node-name=drv0,driver=null-co
> 
> because aio_write_done thinks it's a good idea to use qemu-io's
> BlockBackend -- but when qemu-io is executed through the HMP, the
> BlockBackend is only created for the duration of the qemu-io command
> (unless there already is a BB).  So what I'd have to do is add a
> blk_ref()/blk_unref() there, but for some reason I really don't like that.

What is the reason? If it crashes it should be fixed anyway, I assume?

Fam