[PATCH 2/5] blk-mq: rename hctx_lock & hctx_unlock

[Sagi Grimberg]

On 11/22/21 3:20 PM, Ming Lei wrote:
> On Mon, Nov 22, 2021 at 09:53:53AM +0200, Sagi Grimberg wrote:
>>
>>> -static inline void hctx_unlock(struct blk_mq_hw_ctx *hctx, int srcu_idx)
>>> -	__releases(hctx->srcu)
>>> +static inline void queue_unlock(struct request_queue *q, bool blocking,
>>> +		int srcu_idx)
>>> +	__releases(q->srcu)
>>>    {
>>> -	if (!(hctx->flags & BLK_MQ_F_BLOCKING))
>>> +	if (!blocking)
>>>    		rcu_read_unlock();
>>>    	else
>>> -		srcu_read_unlock(hctx->queue->srcu, srcu_idx);
>>> +		srcu_read_unlock(q->srcu, srcu_idx);
>>
>> Maybe instead of passing blocking bool just look at srcu_idx?
>>
>> 	if (srcu_idx < 0)
>> 		rcu_read_unlock();
>> 	else
>> 		srcu_read_unlock(q->srcu, srcu_idx);
> 
> This way needs to initialize srcu_idx in each callers.

Then look at q->has_srcu that Bart suggested?

> 
>>
>> Or look if the queue has srcu allocated?
>>
>> 	if (!q->srcu)
>> 		rcu_read_unlock();
>> 	else
>> 		srcu_read_unlock(q->srcu, srcu_idx);
> 
> This way is worse since q->srcu may involve one new cacheline fetch.
> 
> hctx->flags is always hot, so it is basically zero cost to check it.

Yea, but the interface is awkward that the caller tells the
routine how it should lock/unlock...