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Date:   Thu, 25 Jan 2018 17:45:19 +0800
From:   Wei Wang <wei.w.wang@intel.com>
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To:     "Michael S. Tsirkin" <mst@redhat.com>
CC:     virtio-dev@lists.oasis-open.org, linux-kernel@vger.kernel.org,
        virtualization@lists.linux-foundation.org, kvm@vger.kernel.org,
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        riel@redhat.com
Subject: Re: [PATCH v24 2/2] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT
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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