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Subject: Re: [PATCH] scsi: Delete scsi_use_blk_mq
From:   John Garry <john.garry@huawei.com>
To:     Bart Van Assche <bvanassche@acm.org>, <jejb@linux.vnet.ibm.com>,
        <martin.petersen@oracle.com>
CC:     <linux-scsi@vger.kernel.org>, <linux-kernel@vger.kernel.org>
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Message-ID: <ca2a7eee-0456-e158-307d-e9b6f32fbefd@huawei.com>
Date:   Tue, 11 Feb 2020 11:53:04 +0000
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On 11/02/2020 11:50, 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.

	          ^ ignore

> 
>>
> 
> Having said all that, I don't feel too strongly about deleting this - 
> it's only some tidy-up.
> 
> Thanks,
> John
> 
> .