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Subject: Re: [PATCH] scsi: fix hung_task when change host from recovery to
 running via sysfs
To:     Benjamin Block <bblock@linux.ibm.com>,
        Ye Bin <yebin@huaweicloud.com>
References: <20230321084204.1860900-1-yebin@huaweicloud.com>
 <20230321142237.GC311313@t480-pf1aa2c2.fritz.box>
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: <641A58D0.1020205@huawei.com>
Date:   Wed, 22 Mar 2023 09:24:32 +0800
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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.
Setting the state of the host to recovery can do this, but I changed the 
state to
running and found that the process could not be woken up.
I don't know what the purpose of designing this sysfs interface was. But 
this
modification can solve the effect I want to achieve.
> For SDEVs we explicitly filter what states can be set from user-space.
> Only `SDEV_RUNNING` and `SDEV_OFFLINE` can be set in
> `store_state_field()`.
>      There is probably quite a few other bad things you can do with this
> interface by using any of the other states used for device destruction
> or EH, and then trigger I/O or said destruction/EH otherwise.
>      Not sure handling this one special case of `SHOST_RECOVERY` is quite
> enough.
>
>
>> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
>> index ee28f73af4d4..ae6b1476b869 100644
>> --- a/drivers/scsi/scsi_sysfs.c
>> +++ b/drivers/scsi/scsi_sysfs.c
>> @@ -216,6 +216,9 @@ store_shost_state(struct device *dev, struct device_attribute *attr,
>>
>>        if (scsi_host_set_state(shost, state))
>>                return -EINVAL;
>> +     else
>> +             wake_up(&shost->host_wait);
>> +
>>        return count;
>>   }
>>
>> --
>> 2.31.1
>>