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

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Message-ID: <ad3804e6-37f8-aa43-19f6-2ef30c0ccca1@oracle.com>
Date:   Wed, 21 Dec 2022 09:40:42 +0000
From:   John Garry <john.g.garry@...cle.com>
To:     Jason Yan <yanaijie@...wei.com>,
        yangxingui <yangxingui@...wei.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 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