Re: [PATCH v2 0/3] scsi: libsas: handle linkrate change in sas_rediscover_dev

[yangxingui <yangxingui@huawei.com>]

On 2026/5/14 17:35, John Garry wrote:
> On 13/05/2026 09:14, yangxingui wrote:
>>
>>
>>
>> On 2026/5/13 15:29, John Garry wrote:
>>> On 13/05/2026 03:16, Xingui Yang wrote:
>>>> When a device attached to an expander phy experiences a linkrate change
>>>> (e.g., due to cable reconnection or negotiation), the current code in
>>>> sas_rediscover_dev() treats it as "broadcast flutter" and takes no 
>>>> action
>>>> if the SAS address and device type remain unchanged.
>>>
>>> Can sas_rediscover_dev() check the linkrate (vs expected) to 
>>> understand that this flutter has renegotiated the linkrate and then 
>>> consider it not just a flutter?
>>
>> Hi, John
>> Theoretically, it is possible. As early as 2019, Jason attempted to 
>> propose the solution you mentioned. He conducted a relatively 
>> comprehensive assessment for flutter, including scenarios where the 
>> SAS address changes or the ATA ID changes. However, in actual use, 
>> such situations almost never occur unless there is an extremely short 
>> time window during which the drive is swapped or a new SATA drive is 
>> replaced. Because this solution is associated with other modifications 
>> and may have significant impacts, it has not been adopted.
>>
>> https://urldefense.com/v3/__https://lore.kernel.org/linux- 
>> scsi/20190130082412.9357-6-yanaijie@huawei.com/__;!!ACWV5N9M2RV99hQ! 
>> K7CIIOxMVXErIMxcZlvm10YX3EVqp0rhSbh_ARyqnaFDmtaqqJtoLTJQui0- 
>> Ox_URh97f8oyREG8htBVo2aC3Ew$
>> Currently, scenarios involving changes in linkrate are relatively more 
>> common, and such situations can be easily reproduced by manually 
>> adjusting the linkrate by sysfs. Therefore, a less impactful 
>> synchronous update solution was adopted.
>>
> 
> What Jason did was to check if same device for flutter, which is not 
> really the same thing as what you want.
> 
> I just don't like these special case callbacks which you propose, as 
> they seem fragile and too specialized.
> 
> Is it possible to just check the linkrate and mark the device as gone 
> and rediscover when this flutter occurs occurs?

Hi, John.
I have updated a new version according to your suggestions.

Thanks,
Xingui
.