linux-kernel - Re: [PATCH v3 1/4] scsi: add expecting_media

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Message-ID: <22533564-9f21-df1a-8cab-7996ccadc788@acm.org>
Date:   Sun, 28 Mar 2021 09:53:15 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Martin Kepplinger <martin.kepplinger@...i.sm>
Cc:     jejb@...ux.ibm.com, linux-kernel@...r.kernel.org,
        linux-scsi@...r.kernel.org, linux-pm@...r.kernel.org,
        martin.petersen@...cle.com, stern@...land.harvard.edu
Subject: Re: [PATCH v3 1/4] scsi: add expecting_media_change flag to error
 path

On 3/28/21 3:25 AM, Martin Kepplinger wrote:
> diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
> index 08c06c56331c..c62915d34ba4 100644
> --- a/drivers/scsi/scsi_error.c
> +++ b/drivers/scsi/scsi_error.c
> @@ -585,6 +585,18 @@ int scsi_check_sense(struct scsi_cmnd *scmd)
>  				return NEEDS_RETRY;
>  			}
>  		}
> +		if (scmd->device->expecting_media_change) {
> +			if (sshdr.asc == 0x28 && sshdr.ascq == 0x00) {
> +				/*
> +				 * clear the expecting_media_change in
> +				 * scsi_decide_disposition() because we
> +				 * need to catch possible "fail fast" overrides
> +				 * that block readahead can cause.
> +				 */
> +				return NEEDS_RETRY;
> +			}
> +		}

Introducing a new state variable carries some risk, namely that a path
that should set or clear the state variable is overlooked. Is there an
approach that does not require to introduce a new state variable, e.g.
to send a REQUEST SENSE command after a resume?

Thanks,

Bart.