Linux Virtualization - Sep 2020 - [PATCH 4/8] vhost scsi: fix cmd completion race

On 2020-09-21 11:23, Mike Christie wrote:
> We might not do the final se_cmd put from vhost_scsi_complete_cmd_work.
> If the last put happens a little later then we could race where
> vhost_scsi_complete_cmd_work does vhost_signal, the guest runs and sends
> more IO, and vhost_scsi_handle_vq runs but does not find any free cmds.
> 
> This patch has us delay completing the cmd until the last lio core ref
> is dropped. We then know that once we signal to the guest that the cmd
> is completed that if it queues a new command it will find a free cmd.
It seems weird to me to see a reference to LIO in the description of a
vhost patch? Since this driver supports more backends than LIO, shouldn't
the patch description be made more generic?

Thanks,

Bart.

On 2020-09-21 19:48, Bart Van Assche wrote:
> On 2020-09-21 11:23, Mike Christie wrote:
>> We might not do the final se_cmd put from vhost_scsi_complete_cmd_work.
>> If the last put happens a little later then we could race where
>> vhost_scsi_complete_cmd_work does vhost_signal, the guest runs and
sends
>> more IO, and vhost_scsi_handle_vq runs but does not find any free cmds.
>>
>> This patch has us delay completing the cmd until the last lio core ref
>> is dropped. We then know that once we signal to the guest that the cmd
>> is completed that if it queues a new command it will find a free cmd.
> 
> It seems weird to me to see a reference to LIO in the description of a
> vhost patch? Since this driver supports more backends than LIO,
shouldn't
> the patch description be made more generic?
Please ignore the above comment.

Bart.