On 6/28/18 1:27 AM, Johannes Thumshirn wrote:
> Hi Ming,
>
> On Thu, Jun 28, 2018 at 11:19:16AM +0800, Ming Lei wrote:
>> + list_for_each_entry(rq, list, queuelist) {
>> BUG_ON(rq->mq_ctx != ctx);
>> - list_del_init(&rq->queuelist);
>> - __blk_mq_insert_req_list(hctx, rq, false);
>> + trace_block_rq_insert(hctx->queue, rq);
>> }
>
> I wonder if we really need the above loop unconditionally. It does
> some BUG_ON() sanity checking (which I hate but it was already there
> so not your problem) and tracing of the request insertion.
We can probably kill that now, but jfyi, this was introduced because
of a specific issue.
> So can we maybe only run this loop if tracing is enabled? Not sure if
> this is possible though. Maybe Steven (Cced) can help here.
Don't think it is, since we can be tracing through a variety of
different ways. I think it's best to leave this as-is. If this
were to be changed, it'd have to be a separate patch anyway,
it should not be mixed up with this change.
It does need the list_splice_tail_init() as others found out,
or you'll leave the source list corrupted.
--
Jens Axboe
