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Subject: Re: [PATCH] scsi: Delete scsi_use_blk_mq
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>
References: <1581355992-139274-1-git-send-email-john.garry@huawei.com>
 <3795ab1d-5282-458b-6199-91e3def32463@acm.org>
From:   John Garry <john.garry@huawei.com>
Message-ID: <2e2ead7d-503e-3881-b837-7c689a4d44c6@huawei.com>
Date:   Tue, 11 Feb 2020 11:50:09 +0000
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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