linux-kernel - Re: [PATCH v3] scsi: sd: fix sd shutdown to issue START STOP UNIT command appropriately

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Message-ID: <325a7f60-955c-4e3d-bd16-e5377462fa33@acm.org>
Date: Mon, 28 Jul 2025 08:47:38 -0700
From: Bart Van Assche <bvanassche@....org>
To: Salomon Dushimirimana <salomondush@...gle.com>
Cc: James.Bottomley@...senpartnership.com, dlemoal@...nel.org,
 ipylypiv@...gle.com, linux-kernel@...r.kernel.org,
 linux-scsi@...r.kernel.org, martin.petersen@...cle.com, vishakhavc@...gle.com
Subject: Re: [PATCH v3] scsi: sd: fix sd shutdown to issue START STOP UNIT
 command appropriately

On 7/24/25 2:45 PM, Salomon Dushimirimana wrote:
> Commit aa3998dbeb3a ("ata: libata-scsi: Disable scsi device
> manage_system_start_stop") enabled libata EH to manage device power mode
> trasitions for system suspend/resume and removed the flag from
> ata_scsi_dev_config. However, since the sd_shutdown() function still
> relies on the manage_system_start_stop flag, a spin-down command is not
> issued to the disk with command "echo 1 > /sys/block/sdb/device/delete"
> 
> sd_shutdown() can be called for both system/runtime start stop
> operations, so utilize the manage_run_time_start_stop flag set in the
> ata_scsi_dev_config and issue a spin-down command during disk removal
> when the system is running. This is in addition to when the system is
> powering off and manage_shutdown flag is set. The
> manage_system_start_stop flag will still be used for drivers that still
> set the flag.
> 
> Fixes: aa3998dbeb3a ("ata: libata-scsi: Disable scsi device manage_system_start_stop")
> Signed-off-by: Salomon Dushimirimana <salomondush@...gle.com>
> ---
> Changes in v3:
> - Removed unnecessary tag
> 
>   drivers/scsi/sd.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> index eeaa6af294b81..282000c761f8e 100644
> --- a/drivers/scsi/sd.c
> +++ b/drivers/scsi/sd.c
> @@ -4173,7 +4173,9 @@ static void sd_shutdown(struct device *dev)
>   	if ((system_state != SYSTEM_RESTART &&
>   	     sdkp->device->manage_system_start_stop) ||
>   	    (system_state == SYSTEM_POWER_OFF &&
> -	     sdkp->device->manage_shutdown)) {
> +	     sdkp->device->manage_shutdown) ||
> +	    (system_state == SYSTEM_RUNNING &&
> +	     sdkp->device->manage_runtime_start_stop)) {
>   		sd_printk(KERN_NOTICE, sdkp, "Stopping disk\n");
>   		sd_start_stop_device(sdkp, 0);
>   	}

Runtime power management is not related at all to deleting a LUN through
sysfs. This patch makes it impossible to understand the sd_shutdown()
implementation without studying the ATA subsystem and its history.
Additionally, this patch makes the documentation of
.manage_runtime_start_stop incorrect.

There are only two drivers that set .manage_runtime_start_stop: libata
and the unmaintained sbp2 driver. Has it been considered to test
sdkp->device->is_ata instead of sdkp->device->manage_runtime_start_stop?

Thanks,

Bart.