RE: [PATCH v3 2/4] scsi: ufs: Fix handling of lrbp->cmd

["hoyoung seo" <hy50.seo@samsung.com>]

> From: Bart Van Assche <bvanassche@acm.org>
> Sent: Wednesday, June 28, 2023 4:54 AM
> To: hoyoung seo <hy50.seo@samsung.com>
> Cc: Arthur.Simchaev@wdc.com; JBottomley@Parallels.com;
> adrian.hunter@intel.com; athierry@redhat.com; avri.altman@wdc.com;
> beanhuo@micron.com; jaegeuk@kernel.org; jejb@linux.ibm.com; linux-
> scsi@vger.kernel.org; martin.petersen@oracle.com;
> quic_asutoshd@quicinc.com; quic_ziqichen@quicinc.com; santoshsy@gmail.com;
> stanley.chu@mediatek.com; cpgs@samsung.com; sc.suh@samsung.com;
> kwmad.kim@samsung.com; kwangwon.min@samsung.com; sh425.lee@samsung.com
> Subject: Re: [PATCH v3 2/4] scsi: ufs: Fix handling of lrbp->cmd
> 
> On 6/26/23 18:26, hoyoung seo wrote:
> > @@ -5408,7 +5406,6 @@ static void ufshcd_release_scsi_cmd(struct ufs_hba
> *hba,
> >   	struct scsi_cmnd *cmd = lrbp->cmd;
> >
> >   	scsi_dma_unmap(cmd);
> > -	lrbp->cmd = NULL;	/* Mark the command as completed. */
> >   	ufshcd_release(hba);
> >   	ufshcd_clk_scaling_update_busy(hba);
> >   }
> >
> > Hi,
> > Is there any reason to delete "lrbp->cmd = NULL"?
> > As far as I know, clear to NULL to indicate that cmd is completed.
> >
> > When the UFS MCQ mode is activated, check that lrbp->cmd is NULL to
> check the completion of the command.
> > https://lore.kernel.org/linux-scsi/f0d923ee1f009f171a55c258d044e814ec0
> > 917ab.1685396241.git.quic_nguyenb@quicinc.com/
> >
> > If there is no special reason, why don't you add "lrb->cmd = NULL" again?
> 
> The lrbp->cmd = NULL assignment has been removed because if it would be
> kept the SCSI error handler would crash if it reuses a SCSI command. See
> also the
> scsi_eh_prep_cmnd() and scsi_eh_restore_cmnd() callers. The MCQ code
> should still work because it uses blk_mq_request_started() to check
> whether or not a request is still active.
> 
> Bart.

Hi,

Thank you for your kind reply.
Let me take a closer look at the code of the scsi layer

Seo.