On Wed, 2018-02-28 at 16:55 +0800, Jianchao Wang wrote: > diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c > index a86df9c..6fa7b0c 100644 > --- a/drivers/scsi/scsi_lib.c > +++ b/drivers/scsi/scsi_lib.c > @@ -191,7 +191,8 @@ 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); > + blk_mq_requeue_request(cmd->request, true); > + put_device(&device->sdev_gendev); > return; > } > spin_lock_irqsave(q->queue_lock, flags);
Anyone who sees the put_device() call that follows the blk_mq_requeue_request() call will wonder why that call occurs there. So I think we need a comment above that call that explains where the matching get_device() call is. For the legacy code path, there is a get_device() call in scsi_prep_fn() but no put_device() call in scsi_unprep_fn() - the matching put_device() calls occur in scsi_end_request() and after blk_requeue_request(). For scsi-mq however there is a get_device() call in scsi_mq_get_budget() and a put_device() call in scsi_mq_put_budget(). So why do we need the put_device() calls after blk_mq_requeue_request() and in the mq path for scsi_end_request()? Thanks, Bart.