linux-kernel - Re: [PATCH] blk-mq: clear active_queues before clearing BLK_MQ_F_TAG_QUEUE

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Date:   Fri, 13 Aug 2021 20:36:44 +0800
From:   "yukuai (C)" <yukuai3@...wei.com>
To:     Ming Lei <ming.lei@...hat.com>
CC:     <axboe@...nel.dk>, <linux-block@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <yi.zhang@...wei.com>
Subject: Re: [PATCH] blk-mq: clear active_queues before clearing
 BLK_MQ_F_TAG_QUEUE_SHARED

Hi, jens

Can you please consider to apply this patch.

By the way, sorry about the wrong email I replied.

Thanks
Kuai

On 2021/08/06 10:25, Ming Lei wrote:
> On Sat, Jul 31, 2021 at 02:21:30PM +0800, Yu Kuai wrote:
>> We run a test that delete and recover devcies frequently(two devices on
>> the same host), and we found that 'active_queues' is super big after a
>> period of time.
>>
>> If device a and device b share a tag set, and a is deleted, then
>> blk_mq_exit_queue() will clear BLK_MQ_F_TAG_QUEUE_SHARED because there
>> is only one queue that are using the tag set. However, if b is still
>> active, the active_queues of b might never be cleared even if b is
>> deleted.
>>
>> Thus clear active_queues before BLK_MQ_F_TAG_QUEUE_SHARED is cleared.
>>
>> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
>> ---
>>   block/blk-mq.c | 6 ++++--
>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/block/blk-mq.c b/block/blk-mq.c
>> index 2c4ac51e54eb..2fe396385a4a 100644
>> --- a/block/blk-mq.c
>> +++ b/block/blk-mq.c
>> @@ -2994,10 +2994,12 @@ static void queue_set_hctx_shared(struct request_queue *q, bool shared)
>>   	int i;
>>   
>>   	queue_for_each_hw_ctx(q, hctx, i) {
>> -		if (shared)
>> +		if (shared) {
>>   			hctx->flags |= BLK_MQ_F_TAG_QUEUE_SHARED;
>> -		else
>> +		} else {
>> +			blk_mq_tag_idle(hctx);
>>   			hctx->flags &= ~BLK_MQ_F_TAG_QUEUE_SHARED;
>> +		}
>>   	}
>>   }
> 
> Looks correct, the only remained queue in tagset has to be idled before
> clearing BLK_MQ_F_TAG_QUEUE_SHARED:
> 
> Reviewed-by: Ming Lei <ming.lei@...hat.com>
> 
> 
> 
> Thanks,
> Ming
> 
> .
>