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Message-ID: <1df01cd0-e56e-b615-9418-e3fd69819798@oracle.com>
Date:   Thu, 23 Mar 2023 11:12:33 -0500
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Subject: Re: [PATCH] scsi: fix hung_task when change host from recovery to
 running via sysfs
To:     "yebin (H)" <yebin10@huawei.com>,
        Benjamin Block <bblock@linux.ibm.com>,
        Ye Bin <yebin@huaweicloud.com>
Cc:     jejb@linux.ibm.com, martin.petersen@oracle.com,
        linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20230321084204.1860900-1-yebin@huaweicloud.com>
 <20230321142237.GC311313@t480-pf1aa2c2.fritz.box>
 <641A58D0.1020205@huawei.com>
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From:   Mike Christie <michael.christie@oracle.com>
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On 3/21/23 8:24 PM, yebin (H) wrote:
> 
> 
> On 2023/3/21 22:22, Benjamin Block wrote:
>> On Tue, Mar 21, 2023 at 04:42:04PM +0800, Ye Bin wrote:
>>> From: Ye Bin <yebin10@huawei.com>
>>>
>>> When do follow test:
>>> Step1: echo  "recovery" > /sys/class/scsi_host/host0/state
>> Hmm, that make me wonder, what potential use-case this is for? Just
>> testing?
> Thank you for your reply.
> Actually, I'm looking for a way to temporarily stop sending IO to the driver.

Is this just for testing something or does a user/app need this
functionality for something?

We used to be able to block specific devices but we removed that.
It was useful for people like us where we need to do some low kernel
testing like testing for how upper layers handle IO hangs, but I
think it was not useful for other users so it was removed.