Re: [PATCHSET #upstream] libata: improve FLUSH error handling

[Tejun Heo <htejun@gmail.com>]

Ric Wheeler wrote:
>>   4. If retried FLUSH fails for something other than device error,
>>      don't keep retrying.  We're likely wasting time.
> 
> Are we sure that it is ever the right thing to do to reissue a flush
> command?
> 
> I am worried that this might be much closer to the media error class of
> device errors than something that will benefit from a retry of any type.

Heh.. yeah, as Alan and Jeff said, that's the spec.  If write failure
occurs during flush, the drive is supposed to stop flushing, remove the
sector from cache and report error to the host.  If the host re-issues
flush, the drive continues flushing after the failed sector.

> Also, I am unclear as to how we measure the progress of the device if
> the flush command has failed?

Yes by reporting the first failing sector.  Probably it's better to test
failed > last_failed than failed == last_failed.

>> as there is a humongous patchset pending review #upstream.  Once this
>> gets acked, I'll move it over to #upstream.  It shouldn't interfere
>> too much anyway.
>>
> We have access to a fair number of flaky drives, I can see if we can
> test some of this...

If you can trigger flush errors, please go ahead.

Thanks.

-- 
tejun