Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
IronPort-SDR: TTsaQgzdbj+tNhEmE5rnt2Lf4aJZ0hMdXpRBkv0bkrI0X7tXlkozCKhvmHrUHFzkpIy+FJRbZp
 nQmPia+FcTPujBVUPaBCQ4q3JeCgLku63VYBOJfnSz3oDgkLR2ntFY7z7wweQ4WOPOU5m5AJz9
 81F316S+1B/FbnEmoe7GQbW7GX/5NxyRgeXv/f/HRNOJyApcQSezBTU59e7sRU4G/o/eEPVX6P
 DKSs+nToVJ+OgtjzIxksOg5iHDgoJbnPCBgmHc2AvZMDdiN+U1Z27eFABFjnZsm3ic4z+jX6Y4
 mKU=
From:   Damien Le Moal <Damien.LeMoal@wdc.com>
To:     Simon Arlott <simon@octiron.net>,
        "James E.J. Bottomley" <jejb@linux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
        "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>
Subject: Re: [PATCH] scsi: sd: stop SSD (non-rotational) disks before reboot
Thread-Topic: [PATCH] scsi: sd: stop SSD (non-rotational) disks before reboot
Thread-Index: AQHWRNgorE8Ue5/pcEOqVFi0S2b5Lw==
Date:   Tue, 30 Jun 2020 01:05:12 +0000
Message-ID: <CY4PR04MB37512529D146054814111270E76F0@CY4PR04MB3751.namprd04.prod.outlook.com>
References: <499138c8-b6d5-ef4a-2780-4f750ed337d3@0882a8b5-c6c3-11e9-b005-00805fc181fe>
 <CY4PR04MB37511505492E9EC6A245CFB1E79B0@CY4PR04MB3751.namprd04.prod.outlook.com>
 <18da4d78-f3df-967f-e7ea-8f2faaa95d6b@0882a8b5-c6c3-11e9-b005-00805fc181fe>
 <CY4PR04MB375112FC181C9A625137DB94E79B0@CY4PR04MB3751.namprd04.prod.outlook.com>
 <fff9e48d-e9a5-632d-5d84-a0aaa68f92a9@0882a8b5-c6c3-11e9-b005-00805fc181fe>
Accept-Language: en-US
Content-Language: en-US
wdcipoutbound: EOP-TRUE
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-MS-Exchange-CrossTenant-Network-Message-Id: 6d6e2ba6-5c46-4f00-b9b0-08d81c91a475
X-MS-Exchange-CrossTenant-originalarrivaltime: 30 Jun 2020 01:05:12.7079
 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: b61c8803-16f3-4c35-9b17-6f65f441df86
X-MS-Exchange-CrossTenant-mailboxtype: HOSTED
X-MS-Exchange-CrossTenant-userprincipalname: j6vfLIRC1cW+MAOxSjT+DO68c2vVf4lbvojMkUg/uUpf1PY0HqAmHZpZYO4KbVyzLZO6U7/+78UwBQVXSj9r6g==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY1PR04MB2220
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 2020/06/29 3:23, Simon Arlott wrote:=0A=
> On 19/06/2020 00:31, Damien Le Moal wrote:=0A=
>> On 2020/06/18 21:26, Simon Arlott wrote:=0A=
>>> I haven't verified it, but the BIOS leaves the power off for several=0A=
>>> seconds which should be long enough for the HDDs to spin down.=0A=
>>>=0A=
>>> I'm less concerned about those suddenly losing power but it would be=0A=
>>> nice to have a stop command sent to them too.=0A=
>>=0A=
>> OK. So maybe the patch should be as simple as changing SYSTEM_RESTART st=
ate to=0A=
>> SYSTEM_POWER_OFF if reboot=3Dp is set, no ? Since that is consistent wit=
h the fact=0A=
>> that reboot=3Dp will cause power to go off, exactly the same as a regula=
r=0A=
>> shutdown, it seems cleaner and safer to use SYSTEM_POWER_OFF for the ent=
ire=0A=
>> system, not just scsi disks.=0A=
> =0A=
> That could be a bit misleading because the power isn't going to stay=0A=
> off. Some of the network drivers have specific WOL behaviour changes=0A=
> for a power off.=0A=
=0A=
The point is that the power goes off, same as for a SYSTEM_POWER_OFF shutdo=
wn.=0A=
It do not think it matters how long it will be off before your BIOS restart=
s the=0A=
laptop power. And actually enabling the NICs WOL function would I think act=
ually=0A=
be a very good thing: if the PSU power cycling fails, the machine can still=
 be=0A=
remotely woken-up as configured by the user.=0A=
=0A=
> Power cycling the PSU is not something that every BIOS will do, so it's=
=0A=
> not that simple. It could be a module parameter but I'd be concerned=0A=
> that some other code will assuming the system should be powered off and=
=0A=
> all of my reboots will become power off events.=0A=
=0A=
Or define a SYSTEM_RESTART_P that essentially does what SYSTEM_POWER_OFF do=
es +=0A=
the addition of telling the BIOS to restart the PSU, if the machines suppor=
ts=0A=
it. What happens if one does a reboot=3Dp on a machine that does not suppor=
t it ?=0A=
Does this become a shutdown, or does it become a normal reset ?=0A=
=0A=
=0A=
-- =0A=
Damien Le Moal=0A=
Western Digital Research=0A=