Re: [PATCH 2/2] scsi: core: decrease scsi_device's iorequest_cnt if dispatch failed

[Ming Lei]

On Mon, May 15, 2023 at 03:01:56PM +0800, Wenchao Hao wrote:
> If scsi_dispatch_cmd() failed, the SCSI command was not sent to the target,
> scsi_queue_rq() would return BLK_STS_RESOURCE and the related request
> would be requeued. The timeout of this request would not fire, no one would
> increase iodone_cnt.
> 
> The above flow would result the iodone_cnt smaller than iorequest_cnt.
> So decrease the iorequest_cnt if dispatch failed to workaround the issue.
> 
> Link:https://lore.kernel.org/linux-scsi/8e0f2d31-e6ff-ec4a-3974-450560ad49c5@xxxxxxxxxx/T/#t
> 
> Signed-off-by: Wenchao Hao <haowenchao2@xxxxxxxxxx>
> ---
>  drivers/scsi/scsi_lib.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 03964b26f3f2..0226c9279cef 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -1485,6 +1485,7 @@ static int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
>  		 */
>  		SCSI_LOG_MLQUEUE(3, scmd_printk(KERN_INFO, cmd,
>  			"queuecommand : device blocked\n"));
> +		atomic_dec(&cmd->device->iorequest_cnt);
>  		return SCSI_MLQUEUE_DEVICE_BUSY;
>  	}
>  
> @@ -1517,6 +1518,7 @@ static int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
>  	trace_scsi_dispatch_cmd_start(cmd);
>  	rtn = host->hostt->queuecommand(host, cmd);
>  	if (rtn) {
> +		atomic_dec(&cmd->device->iorequest_cnt);
>  		trace_scsi_dispatch_cmd_error(cmd, rtn);
>  		if (rtn != SCSI_MLQUEUE_DEVICE_BUSY &&
>  		    rtn != SCSI_MLQUEUE_TARGET_BUSY)

Looks fine, so the command is accounted in case that it is consumed by
scsi stack, otherwise the counter has to be undone.

Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>


Thanks,
Ming