On Fri, 2018-03-02 at 11:31 +0800, Jianchao Wang wrote:
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index a86df9c..d2f1838 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -191,7 +191,13 @@ static void __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, bool unbusy)
> */
> cmd->result = 0;
> if (q->mq_ops) {
> - scsi_mq_requeue_cmd(cmd);
> + /*
> + * scsi_device.sdev_gendev will be get every time in .get_budget and
> + * be put in scsi_end_request. Hence we need to put the reference
> + * here when we decide to requeue request.
> + */
> + blk_mq_requeue_request(cmd->request, true);
> + put_device(&device->sdev_gendev);
> return;
> }
> spin_lock_irqsave(q->queue_lock, flags);
Please consider to change the new comment into something like the following:
"Before a SCSI command is dispatched, get_device(&sdev->sdev_gendev) is called
and the host, target and device busy counters are increased. Since requeuing a
request causes these actions to be repeated and since scsi_device_unbusy() has
already been called, put_device(&device->sdev_gendev) must still be called. Call
put_device() after blk_mq_requeue_request() to avoid that removal of the SCSI
device can start before requeueing has happened."
Thanks,
Bart.
