linux-kernel - Re: [PATCH] scsi: Delete scsi_use_blk

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Date:   Wed, 12 Feb 2020 11:10:44 -0500
From:   "Ewan D. Milne" <emilne@...hat.com>
To:     John Garry <john.garry@...wei.com>,
        Bart Van Assche <bvanassche@....org>,
        jejb@...ux.vnet.ibm.com, martin.petersen@...cle.com
Cc:     linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scsi: Delete scsi_use_blk_mq

On Tue, 2020-02-11 at 11:50 +0000, John Garry wrote:
> On 10/02/2020 22:37, Bart Van Assche wrote:
> > On 2/10/20 9:33 AM, John Garry wrote:
> > > -module_param_named(use_blk_mq, scsi_use_blk_mq, bool, S_IWUSR | 
> > > S_IRUGO);
> 
> Hi Bart,
> 
> > Will this change cause trouble to shell scripts that set or read this 
> > parameter (/sys/module/scsi_mod/parameters/use_blk_mq)? 
> 
> The entry in Documentation/admin-guide/kernel-parameters.txt is gone for 
> 2 years now.
> 
> And it is not an archaic module param, it was introduced 6 years ago. As 
> such, I'd say that if a shell script was setup to access this parameter, 
> then it would prob also pre-check if it exists and gracefully accept 
> that it may not.
> 
> I will also note that there is still scsi_sysfs.c:show_use_blk_mq(), 
> which would stay.
> 
> What will the
> > impact be on systems where scsi_mod.use_blk_mq=Y is passed by GRUB to 
> > the kernel at boot time, e.g. because it has been set in the 
> > GRUB_CMDLINE_LINUX variable in /etc/default/grub?
> 
> The kernel should any params that does not recognize.
> 
> 
> Having said all that, I don't feel too strongly about deleting this - 
> it's only some tidy-up.
> 
> Thanks,
> John
> 

I think we should remove it.  It is not good to have a kernel parameter
that people used to be able to set to "N" that no longer does that.

-Ewan