Re: [PATCH] ufs: core: Disable queue depth tracking support

[Leon Romanovsky <leon@kernel.org>]

On Fri, Aug 14, 2026 at 02:49:47PM -0700, Bart Van Assche wrote:
> Disable queue depth tracking support because:
>  - UFS devices shouldn't need queue tracking support. If the host sends
>    less than or equal to bQueueDepth commands to the UFS device, no TASK
>    SET FULL condition should be reported. If a TASK SET FULL condition
>    is reported anyway, the host->host_blocked variable will be set and
>    the SCSI command will be requeued. Submission of the SCSI command
>    will be retried after another SCSI command has completed.
>  - The queue depth tracking code is not thread-safe. With MCQ enabled,
>    scsi_track_queue_full() may be called from multiple CPU cores
>    concurrently. This is not safe because individual
>    scsi_track_queue_full() calls are not serialized.
>  - scsi_track_queue_full() is called from interrupt context but not all
>    code called by scsi_track_queue_full() is IRQ-safe. Here is an
>    example of a call chain that may cause interrupts to be enabled,
>    something that is not allowed from interrupt context:
> 
>    ufshcd_mcq_poll_cqe_lock()
>      ufshcd_compl_one_cqe()
>        scsi_done()
>          blk_mq_complete_request()
>            scsi_complete()
>              scsi_decide_disposition()
>                scsi_handle_queue_full()
>                  scsi_track_queue_full()
>                    scsi_change_queue_depth()
>                      blk_set_queue_depth()
>                        rq_qos_queue_depth_changed()
>                          ioc_rqos_queue_depth_changed()
>                            spin_lock_irq()
>                            spin_unlock_irq() <- enables interrupts
> 
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> ---
>  drivers/infiniband/ulp/srp/ib_srp.c |  4 ++++
>  drivers/ufs/core/ufshcd.c           | 16 ----------------
>  2 files changed, 4 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
> index acbd787de265..19a6400d1ec4 100644
> --- a/drivers/infiniband/ulp/srp/ib_srp.c
> +++ b/drivers/infiniband/ulp/srp/ib_srp.c
> @@ -1044,6 +1044,10 @@ static void srp_remove_target(struct srp_target_port *target)
>  	WARN_ON_ONCE(target->state != SRP_TARGET_REMOVED);
>  
>  	srp_del_scsi_host_attr(target->scsi_host);
> +	/*
> +	 * The srp_remove_host() call decrements the rport reference count.
> +	 * Keep the rport as long as its needed.
> +	 */

I believe we can drop this comment and keep the patch limited
to drivers/ufs/core/ufshcd.c only.

Thanks