Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH V9 1/4] blk-mq: insert to hctx dispatch list when
 bypass_insert is true
To:     Jens Axboe <axboe@kernel.dk>
Cc:     ming.lei@redhat.com, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <1543995842-20704-1-git-send-email-jianchao.w.wang@oracle.com>
 <1543995842-20704-2-git-send-email-jianchao.w.wang@oracle.com>
 <54c7377f-e8e6-92cf-eced-6c76297afd52@kernel.dk>
From:   "jianchao.wang" <jianchao.w.wang@oracle.com>
Message-ID: <99339021-4d05-8dff-bee4-a6af2eaf3e21@oracle.com>
Date:   Thu, 6 Dec 2018 09:12:02 +0800
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.2.1
MIME-Version: 1.0
In-Reply-To: <54c7377f-e8e6-92cf-eced-6c76297afd52@kernel.dk>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


On 12/6/18 12:25 AM, Jens Axboe wrote:
> On 12/5/18 12:43 AM, Jianchao Wang wrote:
>> We don't allow direct dispatch of anything but regular reads/writes
>> and insert all of non-read-write requests. However, this is not
>> correct for 'bypass_insert == true' case where inserting is ignored
>> and BLK_STS_RESOURCE is returned. The caller will fail forever.
>>
>> Fix it with inserting the non-read-write request to hctx dispatch
>> list to avoid to involve merge and io scheduler when bypass_insert
>> is true.
>>
>> Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com>
>> ---
>>  block/blk-mq.c | 19 +++++++++++++++++--
>>  1 file changed, 17 insertions(+), 2 deletions(-)
>>
>> diff --git a/block/blk-mq.c b/block/blk-mq.c
>> index 9005505..153af90 100644
>> --- a/block/blk-mq.c
>> +++ b/block/blk-mq.c
>> @@ -1822,6 +1822,7 @@ static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
>>  {
>>  	struct request_queue *q = rq->q;
>>  	bool run_queue = true;
>> +	bool force = false;
>>  
>>  	/*
>>  	 * RCU or SRCU read lock is needed before checking quiesced flag.
>> @@ -1836,9 +1837,19 @@ static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
>>  		goto insert;
>>  	}
>>  
>> -	if (!blk_rq_can_direct_dispatch(rq) || (q->elevator && !bypass_insert))
>> +	if (q->elevator && !bypass_insert)
>>  		goto insert;
>>  
>> +	if (!blk_rq_can_direct_dispatch(rq)) {
>> +		/*
>> +		 * For 'bypass_insert == true' case, insert request into hctx
>> +		 * dispatch list.
>> +		 */
>> +		if (bypass_insert)
>> +			force = true;
>> +		goto insert;
>> +	}
> 
> Just do force = bypass_insert, no need for the if.
> 

Yes, I will do it.

Thanks
Jianchao