[PATCH 3/5] blk-mq: add helper of blk_mq_global_quiesce_wait()

[Sagi Grimberg]

On 11/22/21 9:56 AM, Sagi Grimberg wrote:
> 
>> Add helper of blk_mq_global_quiesce_wait() for supporting to quiesce
>> queues in parallel, then we can just wait once if global quiesce wait
>> is allowed.
> 
> blk_mq_global_quiesce_wait() is a poor name... global is scope-less and
> obviously it has a scope.
> 
> 
>> Signed-off-by: Ming Lei <ming.lei at redhat.com>
>> ---
>>   include/linux/blk-mq.h | 13 +++++++++++++
>>   1 file changed, 13 insertions(+)
>>
>> diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
>> index 5cc7fc1ea863..a9fecda2507e 100644
>> --- a/include/linux/blk-mq.h
>> +++ b/include/linux/blk-mq.h
>> @@ -777,6 +777,19 @@ static inline bool blk_mq_add_to_batch(struct 
>> request *req,
>>       return true;
>>   }
>> +/*
>> + * If the queue has allocated & used srcu to quiesce queue, quiesce 
>> wait is
>> + * done via the synchronize_srcu(q->rcu), otherwise it is done via 
>> global
>> + * synchronize_rcu().
>> + *
>> + * This helper can help us to support quiescing queue in parallel, so 
>> just
>> + * one quiesce wait is enough if global quiesce wait is allowed.
>> + */
>> +static inline bool blk_mq_global_quiesce_wait(struct request_queue *q)
>> +{
>> +    return !q->alloc_srcu;

	return !q->srcu ?