linux-kernel - Re: [PATCH V2] scsi: libsas: Directly kick-off EH when ATA device fell off

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Message-ID: <8dd5a132-9b58-6cde-e596-de15cdfa96db@huawei.com>
Date:   Tue, 20 Dec 2022 10:34:04 +0800
From:   yangxingui <yangxingui@...wei.com>
To:     John Garry <john.g.garry@...cle.com>, <jejb@...ux.ibm.com>,
        <martin.petersen@...cle.com>, <damien.lemoal@...nsource.wdc.com>,
        <linux-ide@...r.kernel.org>, <hare@...e.com>, <hch@....de>
CC:     <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linuxarm@...wei.com>, <prime.zeng@...ilicon.com>,
        <kangfenglong@...wei.com>
Subject: Re: [PATCH V2] scsi: libsas: Directly kick-off EH when ATA device
 fell off



On 2022/12/19 22:53, John Garry wrote:
> On 19/12/2022 12:59, yangxingui wrote:
>>> Firstly, I think that there is a bug in sas_ata_device_link_abort() 
>>> -> ata_link_abort() code in that the host lock in not grabbed, as the 
>>> comment in ata_port_abort() mentions. Having said that, libsas had 
>>> already some dodgy host locking usage - specifically dropping the 
>>> lock for the queuing path (that's something else to be fixed up ... I 
>>> think that is due to queue command CB calling task_done() in some 
>>> cases), but I still think that sas_ata_device_link_abort() should be 
>>> fixed (to grab the host lock).
>> ok, I agree with you very much for this, I had doubts about whether we 
>> needed to grab lock before.
> 
> ok, I hope that you can fix this up separately.
> 
>>>
>>> Secondly, this just seems like a half solution to the age-old problem 
>>> - that is, EH eventually kicking in only after 30 seconds when a disk 
>>> is removed with active IO. I say half solution as SAS disks still 
>>> have this issue for libsas. Can we instead push to try to solve both 
>>> of them now?
>>
>> Jason said you must have such an opinion "a half solution". As libsas 
>> does not have any interface to mark all outstanding commands as failed 
>> for SAS disk currently and SAS disk support I/O resumable transmission 
>> after intermittent disconnections
> 
> I don't know what you mean by "resumable transmission after intermittent 
> disconnections".
I mean if sas disk plug-in in 2 seconds after plug-out with power 
supply. sas disk can continue response for the active io.
such as: disk's phy up in 2 seconds after phy down.
> 
>> , so I want to optimize sata disk first.
>> If we want to achieve a complete solution, perhaps we need to define 
>> such an interface in libsas and implement it by lldd. My current idea 
>> is to call sas_abort_task() for all outstanding commands in lldd. I 
>> wonder if you approve of this?
> 
> Are you sure you mean sas_abort_task()? That is for the LLDD to issue an 
> abort TMF. I assume that you mean sas_task_abort(). If so, I am not too 

Yes, I mean sas_task_abort(), the two function names are confusing to 
me. ^_^
> keen on the idea of libsas calling into the LLDD to inform of such an 
> event. Note that maybe a tagset iter function could be used by libsas to 
> abort each active IO, but I don't like libsas messing with such a thing; 
> in addition, there may be some conflict between libsas aborting the IO 
> and the IO completing with error in the LLDD.

I agree with you. Since we have a ready-made interface for mark all 
acive io to failed for sata disks, it may be easier to optimize sata 
disks first. If we don't implement similar interfaces in libsas or lldd, 
what good suggestions do you have?

Thanks,
Xingui
> 
> Please note that I need to refresh my memory on this whole EH topic...
> 
> Thanks,
> John
> 
> .