Hi Bart Thanks for your kindly response and precious time to review this. On 02/28/2018 01:18 AM, Bart Van Assche wrote: > On Tue, 2018-02-27 at 17:06 +0000, Bart Van Assche wrote: >> On Tue, 2018-02-27 at 13:15 +0800, jianchao.wang wrote: >>> Can you share more details about this ? >> >> After having had another look, I think your patch is fine. > > (replying to my own e-mail) > > What I think is fine in your patch is that it skips the unprep and reprep > when requeueing. However, there is a put_device(&sdev->sdev_gendev) call > in scsi_mq_requeue_cmd() and your patch causes that put_device() call to > be skipped when requeueing. An explanation is needed in the commit message > why you think that removing that put_device() call is fine. Your concern is right. For the block legacy path in scsi core, the get_device(&sdev->sdev_gendev) is in prep. So when it requeue the request w/ RQF_DONTPREP, the reference will not be got again. However, for blk-mq patch in scsi core, the get_device(&sdev->sdev_gendev) in .get_budget, so put_device is still needed here. Thanks for your directive. Jianchao
