Re: [PATCH v24 2/2] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT

[Wei Wang <wei.w.wang@intel.com>]

On 01/25/2018 01:15 AM, Michael S. Tsirkin wrote:
> On Wed, Jan 24, 2018 at 06:42:42PM +0800, Wei Wang wrote:
> >   
> >
> > What is this doing? Basically handling the case where vq is broken?
> > It's kind of ugly to tweak feature bits, most code assumes they never
> > change.  Please just return an error to caller instead and handle it
> > there.
> >
> > You can then avoid sprinking the check for the feature bit
> > all over the code.
>
> One thing I don't like about this one is that the previous request
> will still try to run to completion.
>
> And it all seems pretty complex.
>
> How about:
> - pass cmd id to a queued work
> - queued work gets that cmd id, stores a copy and uses that,
>    re-checking periodically - stop if cmd id changes:
>    will replace  report_free_page too since that's set to
>    stop.
>
> This means you do not reuse the queued cmd id also
> for the buffer - which is probably for the best.

Thanks for the suggestion. Please have a check how it's implemented in v25.
Just a little reminder that work queue has internally ensured that there 
is no re-entrant of the same queued function.

Best,
Wei