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Date:   Wed, 21 Dec 2022 09:40:42 +0000
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Subject: Re: [PATCH V2] scsi: libsas: Directly kick-off EH when ATA device
 fell off
To:     Jason Yan <yanaijie@huawei.com>,
        yangxingui <yangxingui@huawei.com>, jejb@linux.ibm.com,
        martin.petersen@oracle.com, damien.lemoal@opensource.wdc.com,
        linux-ide@vger.kernel.org, hare@suse.com, hch@lst.de
Cc:     linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org,
        linuxarm@huawei.com, prime.zeng@hisilicon.com,
        kangfenglong@huawei.com
References: <20221216100327.7386-1-yangxingui@huawei.com>
 <565fcf28-ec53-8d74-00a3-94be8e5b60e4@oracle.com>
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From:   John Garry <john.g.garry@oracle.com>
Organization: Oracle Corporation
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On 20/12/2022 09:49, Jason Yan wrote:
> 
> Itering tagset in libsas is odd.

Itering with block layer APIs is just a method to deal with each active 
IO. However, libsas should not be aborting IO directly. It may provide 
helper routines, but the LLDD should be dealing with aborting IO.

 >
 > The question is, shall we implement the aborting from the driver side,
 > such as what sas_ata_device_link_abort() do. Or shall we implement the
 > aborting from the upper side(scsi middle layer or block layer), such as
 > trigger block layer time out handler immediately after we found device
 > is gone?

As mentioned, aborting each IO should be the job of the LLDD. However, 
just making the IO timeout will lead to EH kicking in earlier, and EH 
will do usual per-IO handling in sas_eh_handle_sas_errors() that would 
happen when the IO timesout normally - so what are we really gaining 
here? Just EH kicks in earlier. But we still have the problem of all 
other per-host IO being blocked while EH is active.

Thanks,
John