Re: [PATCH 8/8] blk-mq: support per-distpatch_queue flush machinery

[Ming Lei]

On Wed, Sep 10, 2014 at 2:48 AM, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
>> +     if (hctx) {
>> +             int cmd_sz = q->tag_set->cmd_size;
>> +             int node = hctx->numa_node;
>> +
>> +             fq = kzalloc_node(sizeof(*fq), GFP_KERNEL, node);
>> +             if (!fq)
>> +                     goto failed;
>> +
>> +             rq_sz = round_up(rq_sz + cmd_sz, cache_line_size());
>> +             fq->flush_rq = kzalloc_node(rq_sz, GFP_KERNEL, node);
>> +             if (!fq->flush_rq)
>> +                     goto rq_failed;
>> +
>> +             spin_lock_init(&fq->mq_flush_lock);
>> +     } else {
>> +             fq = kzalloc(sizeof(*fq), GFP_KERNEL);
>> +             if (!fq)
>> +                     goto failed;
>> +
>> +             fq->flush_rq = kzalloc(rq_sz, GFP_KERNEL);
>> +             if (!fq->flush_rq)
>> +                     goto rq_failed;
>> +     }
>
> Seems like this would be a lot cleaner by passing the cmd_size and
> node_id explicitly.  The added benefit would be that we could also
> pass the node for the blk_init_queue_node() case.

OK.

>
>> +static void __blk_mq_exit_flush(struct request_queue *q,
>> +             unsigned free_end, unsigned int exit_end)
>> +{
>> +     struct blk_mq_hw_ctx *hctx;
>> +     unsigned int k;
>> +     struct blk_flush_queue *fq;
>> +     struct blk_mq_tag_set *set = q->tag_set;
>> +     unsigned start_idx = set->queue_depth;
>> +
>> +     queue_for_each_hw_ctx(q, hctx, k) {
>> +             if (k >= free_end)
>> +                     break;
>> +
>> +             fq = hctx->fq;
>> +             if (k < exit_end && set->ops->exit_request)
>> +                     set->ops->exit_request(set->driver_data,
>> +                                     fq->flush_rq, k,
>> +                                     start_idx + k);
>> +
>> +             blk_free_flush_queue(fq);
>> +     }
>
> Can we merge the mq init/exit case into some existing for each hctx
> loop in blk-mq?

I am wondering we can do that because lifetime is totally different
between flush requests and tag_set requests which are initialized
before request queue is created.

Thanks,
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