Re: [PATCH V2 3/3] ublk_drv: do not add a re-issued request aborted previously to ioucmd's task_work

[Ming Lei <ming.lei@redhat.com>]

On Mon, Aug 15, 2022 at 10:36:33AM +0800, ZiyangZhang wrote:
> In ublk_queue_rq(), Assume current request is a re-issued request aborted
> previously in monitor_work because the ubq_daemon(ioucmd's task) is
> PF_EXITING. For this request, we cannot call
> io_uring_cmd_complete_in_task() anymore because at that moment io_uring
> context may be freed in case that no inflight ioucmd exists. Otherwise,
> we may cause null-deref in ctx->fallback_work.
> 
> Add a check on UBLK_IO_FLAG_ABORTED to prevent the above situation. This
> check is safe and makes sense.
> 
> Note: monitor_work sets UBLK_IO_FLAG_ABORTED and ends this request
> (releasing the tag). Then the request is restarted(allocating the tag)
> and we are here. Since releasing/allocating a tag implies smp_mb(),
> finding UBLK_IO_FLAG_ABORTED guarantees that here is a re-issued request
> aborted previously.
> 
> Suggested-by: Ming Lei <ming.lei@redhat.com>
> Signed-off-by: ZiyangZhang <ZiyangZhang@linux.alibaba.com>

Reviewed-by: Ming Lei <ming.lei@redhat.com>


Thanks,
Ming