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

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Date:   Mon, 19 Dec 2022 23:28:47 +0800
From:   Jason Yan <yanaijie@...wei.com>
To:     John Garry <john.g.garry@...cle.com>,
        Xingui Yang <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 2022/12/19 17:23, John Garry wrote:
> On 16/12/2022 10:03, Xingui Yang wrote:
>> If the ATA device fell off, call sas_ata_device_link_abort() directly and
>> mark all outstanding QCs as failed and kick-off EH Immediately. This 
>> avoids
>> having to wait for block layer timeouts.
>>
>> Signed-off-by: Xingui Yang <yangxingui@...wei.com>
>> ---
>> Changes to v1:
>> - Use dev_is_sata() to check ATA device type
>>   drivers/scsi/libsas/sas_discover.c | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/scsi/libsas/sas_discover.c 
>> b/drivers/scsi/libsas/sas_discover.c
>> index d5bc1314c341..a12b65eb4a2a 100644
>> --- a/drivers/scsi/libsas/sas_discover.c
>> +++ b/drivers/scsi/libsas/sas_discover.c
>> @@ -362,6 +362,9 @@ static void sas_destruct_ports(struct asd_sas_port 
>> *port)
>>   void sas_unregister_dev(struct asd_sas_port *port, struct 
>> domain_device *dev)
>>   {
>> +    if (test_bit(SAS_DEV_GONE, &dev->state) && dev_is_sata(dev))
>> +        sas_ata_device_link_abort(dev, false);
> 
> 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 

Taking big locks in queuing path is not a good idea. This will bring 
down performance.


> 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).

For sas_ata_device_link_abort(), it should grab ap->lock.

Thanks,
Jason