Re: [PATCH 1/5] blk-mq: move srcu from blk_mq_hw_ctx to request_queue

Ming Lei
2021-11-19T08:10:32Z

On Thu, Nov 18, 2021 at 08:30:49PM -0800, Bart Van Assche wrote:
> On 11/18/21 18:18, Ming Lei wrote:
> > + bool alloc_srcu;
>
> I found the following statement multiple times in this patch:
>
> WARN_ON_ONCE(q->alloc_srcu != !!(q->tag_set->flags & BLK_MQ_F_BLOCKING));
>
> Does this mean that the new q->alloc_srcu member variable can be left out
> and that it can be replaced with the following test?
>
> q->tag_set->flags & BLK_MQ_F_BLOCKING

q->tag_set can't be used anymore after blk_cleanup_queue() returns,
and we need the flag for freeing request_queue instance.

>
> Please note that I'm not concerned about the memory occupied by this
> variable but only about avoiding redundancy.
>
> If this variable is retained it probably should be renamed, e.g. "has_srcu"
> instead of "alloc_srcu".

Fine.

Thanks,
Ming