linux-kernel - Re: [PATCH (v2)] scsi: sd: add parameter to stop disks before reboot

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Message-ID: <20200629080947.GA28551@infradead.org>
Date:   Mon, 29 Jun 2020 09:09:47 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     Simon Arlott <simon@...iron.net>
Cc:     "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Jonathan Corbet <corbet@....net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-scsi@...r.kernel.org, linux-doc@...r.kernel.org,
        Bart Van Assche <bvanassche@....org>,
        Christoph Hellwig <hch@...radead.org>,
        Damien Le Moal <Damien.LeMoal@....com>,
        Pavel Machek <pavel@....cz>,
        Henrique de Moraes Holschuh <hmh@....eng.br>
Subject: Re: [PATCH (v2)] scsi: sd: add parameter to stop disks before reboot

On Sun, Jun 28, 2020 at 07:32:51PM +0100, Simon Arlott wrote:
> I need to use "reboot=p" on my desktop because one of the PCIe devices
> does not appear after a warm boot. This results in a very cold boot
> because the BIOS turns the PSU off and on.
> 
> The scsi sd shutdown process does not send a stop command to disks
> before the reboot happens (stop commands are only sent for a shutdown).
> 
> The result is that all of my SSDs experience a sudden power loss on
> every reboot, which is undesirable behaviour because it could cause data
> to be corrupted. These events are recorded in the SMART attributes.
> 
> Add a "stop_before_reboot" module parameter that can be used to control
> the shutdown behaviour of disks before a reboot. The default will be
> the existing behaviour (disks are not stopped).
> 
>   sd_mod.stop_before_reboot=<integer>
>     0 = disabled (default)
>     1 = enabled
> 
> The behaviour on shutdown is unchanged: all disks are unconditionally
> stopped.

What happened to the suggestion to treat reboot=p like a poweroff
instead?  That seems to be fundamentally the right thing to do.