linux-kernel - Re: [PATCH 1/2] blk-mq: add two interfaces to lock/unlock blk_mq

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Message-ID: <115d97bf-8c7f-44e5-7665-9f7f2c8c3c2b@huawei.com>
Date:   Mon, 9 Aug 2021 09:11:04 +0800
From:   "yukuai (C)" <yukuai3@...wei.com>
To:     Bart Van Assche <bvanassche@....org>, <axboe@...nel.dk>,
        <josef@...icpanda.com>, <ming.lei@...hat.com>
CC:     <linux-block@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <nbd@...er.debian.org>, <yi.zhang@...wei.com>
Subject: Re: [PATCH 1/2] blk-mq: add two interfaces to lock/unlock
 blk_mq_tags->lock

On 2021/08/09 0:44, Bart Van Assche wrote:
> On 8/7/21 8:17 PM, Yu Kuai wrote:
>> +void blk_mq_tags_lock(struct blk_mq_tags *tags, unsigned long *flags)
>> +{
>> +	spin_lock_irqsave(&tags->lock, *flags);
>> +}
>> +EXPORT_SYMBOL(blk_mq_tags_lock);
>> +
>> +void blk_mq_tags_unlock(struct blk_mq_tags *tags, unsigned long *flags)
>> +{
>> +	spin_unlock_irqrestore(&tags->lock, *flags);
>> +}
>> +EXPORT_SYMBOL(blk_mq_tags_unlock);
> 
> The tag map lock is an implementation detail and hence this lock must
> not be used directly by block drivers. I propose to introduce and export
> a new function to block drivers that does the following:
> * Lock tags->lock.
> * Call blk_mq_tag_to_rq().
> * Check whether the request is in the started state. If so, increment
> its reference count.
> * Unlock tags->lock.

Hi, Bart

Thanks for your advice, will do this in next iteration.

Best regards
Kuai