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

Martin K. Petersen
2018-03-02T01:43:08Z

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.

Thanks!

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Martin K. Petersen Oracle Linux Engineering