Re: [PATCH v2 2/2] scsi: ufs: core: Decouple CQ sweep from request iterator in MCQ

[Bart Van Assche]

On 9/18/26 7:38 AM, Stanley Jhu wrote:
> In MCQ mode, ufshcd_mcq_compl_pending_transfer() uses
> blk_mq_tagset_busy_iter() to iterate over busy requests during error
> recovery and host reset. However, both iterator callbacks perform
> whole-queue operations redundantly for each visited request:
>
> - force_compl == true: ufshcd_mcq_force_compl_one() calls
>    ufshcd_mcq_compl_all_cqes_lock() on every busy request, sweeping the
>    entire completion ring (hwq->max_entries slots) once per active
>    request under spin_lock_irqsave even though the first sweep already
>    cleared all completion entries.
> - force_compl == false: ufshcd_mcq_compl_one() acquires cq_lock and
>    polls CQTPy over MMIO via ufshcd_mcq_poll_cqe_lock() for every busy
>    request without doing any per-request work.
>
> Sweep or poll each hardware queue (hba->uhq[i]) once at the start of
> ufshcd_mcq_compl_pending_transfer(). When force_compl is true, run
> blk_mq_tagset_busy_iter() afterward to complete residual in-flight
> requests with DID_REQUEUE, and remove the now-unused
> ufshcd_mcq_compl_one() callback.

Forcibly completing SCSI commands from inside the UFS SCSI host reset
error handling callback is incompatible with the SCSI core error
handler. The "force_compl" behavior should be removed instead of
reworking it. If you take a look at the SDB (single doorbell) code you
will see that forcibly completing requests doesn't happen for SDB mode.

Bart.