Re: [PATCH 2/3] scsi: core: Retry after a delay if the device is becoming ready

From: Ming Lei <ming.lei@redhat.com>
To: Bart Van Assche <bvanassche@acm.org>
Cc: "Martin K . Petersen" <martin.petersen@oracle.com>,
	Jaegeuk Kim <jaegeuk@kernel.org>,
	linux-scsi@vger.kernel.org, Hannes Reinecke <hare@suse.de>,
	John Garry <john.garry@huawei.com>
Subject: Re: [PATCH 2/3] scsi: core: Retry after a delay if the device is becoming ready
Date: Wed, 29 Jun 2022 09:21:55 +0800	[thread overview]
Message-ID: <YrupM8k8uG3HIRmt@T590> (raw)
In-Reply-To: <20220628222131.14780-3-bvanassche@acm.org>

On Tue, Jun 28, 2022 at 03:21:30PM -0700, Bart Van Assche wrote:
> If a logical unit reports that it is becoming ready, retry the command
> after a delay instead of retrying immediately.
> 
> Cc: Ming Lei <ming.lei@redhat.com>
> Cc: Hannes Reinecke <hare@suse.de>
> Cc: John Garry <john.garry@huawei.com>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> ---
>  drivers/scsi/scsi_error.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
> index 49ef864df581..fb7e363c4c00 100644
> --- a/drivers/scsi/scsi_error.c
> +++ b/drivers/scsi/scsi_error.c
> @@ -625,10 +625,10 @@ enum scsi_disposition scsi_check_sense(struct scsi_cmnd *scmd)
>  			return NEEDS_RETRY;
>  		/*
>  		 * if the device is in the process of becoming ready, we
> -		 * should retry.
> +		 * should retry after a delay.
>  		 */
>  		if ((sshdr.asc == 0x04) && (sshdr.ascq == 0x01))
> -			return NEEDS_RETRY;
> +			return ADD_TO_MLQUEUE;

The above code & commit log just said changing to retry after a delay, but not
explains why, care to document reason why the delay is useful?

Thanks
Ming