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Subject: Re: [PATCH] scsi: fix hung_task when change host from recovery to
 running via sysfs
To:     Mike Christie <michael.christie@oracle.com>,
        Benjamin Block <bblock@linux.ibm.com>,
        Ye Bin <yebin@huaweicloud.com>
References: <20230321084204.1860900-1-yebin@huaweicloud.com>
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 <641A58D0.1020205@huawei.com>
 <1df01cd0-e56e-b615-9418-e3fd69819798@oracle.com>
CC:     <jejb@linux.ibm.com>, <martin.petersen@oracle.com>,
        <linux-scsi@vger.kernel.org>, <linux-kernel@vger.kernel.org>
From:   "yebin (H)" <yebin10@huawei.com>
Message-ID: <641CFFDC.2040201@huawei.com>
Date:   Fri, 24 Mar 2023 09:41:48 +0800
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On 2023/3/24 0:12, Mike Christie wrote:
> 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?

This can be used to store IO in the block layer, enabling some fault recovery
that is insensitive to the upper layer.Also want to use this state to test the
block layer.

> 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.
>
> .
>