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

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Message-ID: <a2ca30e4-a7fe-cae9-7a71-b54ae076170d@huawei.com>
Date:   Wed, 21 Dec 2022 17:28:23 +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".
> 
>> , 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 
> keen on the idea of libsas calling into the LLDD to inform of such an 
> event.
I've implemented this solution. The verification seems to be ok both for 
sas/sata device. I'll update the version again. Please have a look?

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