Re: [PATCH V2] scsi: core: use blk_mq_requeue_request in __scsi_queue_insert

jianchao.wang
2018-03-02T02:17:24Z

Hi martin

Thanks for your kindly response.

On 03/02/2018 09:43 AM, Martin K. Petersen wrote:
>
> Jianchao,
>
>> Yes, the block layer core guarantees that scsi_mq_get_budget() will be
>> called before scsi_queue_rq(). I think the full picture is as follows:
>
>> * Before scsi_queue_rq() calls .queuecommand(), get_device() is called for the
>> SCSI device and the device, target and host busy counters are incremented.
>> * If the SCSI core decides to requeue a command, scsi_queue_insert() causes
>> __scsi_queue_insert() to call scsi_device_unbusy(). That last function
>> decreases the device, target and host busy counters but not put_device(sdev).
>> Hence the need for a separate put_device() call after requeuing.
>>
>> It's unfortunate that the SCSI core became so asymmetric. Anyway,
>> since I am now convinced that this patch is correct, feel free to add:
>
> Please add something akin to Bart's explanation as a comment and repost.

yes, sure.

Thanks
Jianchao