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

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