Re: [PATCH 3/3] blk-mq: Use llist_head for blk_cpu_done

[Christoph Hellwig]

On Mon, Jan 25, 2021 at 09:32:04AM +0100, Sebastian Andrzej Siewior wrote:
> On 2021-01-25 08:30:12 [+0000], Christoph Hellwig wrote:
> > > +static void blk_mq_complete_send_ipi(struct request *rq)
> > > +{
> > > + struct llist_head *list;
> > > + unsigned int cpu;
> > > +
> > > + cpu = rq->mq_ctx->cpu;
> > > + list = &per_cpu(blk_cpu_done, cpu);
> > > + if (llist_add(&rq->ipi_list, list)) {
> > > +         INIT_CSD(&rq->csd, __blk_mq_complete_request_remote, rq);
> > > +         smp_call_function_single_async(cpu, &rq->csd);
> > > + }
> > > +}
> > 
> > Nit: it would be nice to initialize cpu and list in the declaration
> > lines.
> 
> Why? They get initialized later.

Because:

        unsigned int cpu = rq->mq_ctx->cpu;
        struct llist_head *list = &per_cpu(blk_cpu_done, cpu);

is a lot easier to follow than:

        struct llist_head *list;
        unsigned int cpu;

        cpu = rq->mq_ctx->cpu;
        list = &per_cpu(blk_cpu_done, cpu);