Re: [PATCH 12/12] libata: implement EH fast drain

[Jeff Garzik <jeff@garzik.org>]

Tejun Heo wrote:
> In most cases, when EH is scheduled, all in-flight commands are
> aborted causing EH to kick in immediately.  However, in some cases
> (especially with PMP), it's unclear which commands are affected by the
> error condition and although aborting all in-flight commands work, it
> isn't optimal and may cause unnecessary disruption.  On the other
> hand, waiting for in-flight commands to drain themselves can take up
> to 30seconds.
> 
> This patch implements EH fast drain to handle such situations.  It
> gives in-flight commands some time to finish up but doesn't wait for
> too long.  After EH is scheduled, fast drain timer is started and if
> no other completion occurs in ATA_EH_FASTDRAIN_INTERVAL all in-flight
> commands are aborted.  If any completion occurred in the interval, the
> port is given another interval to finish up itself.
> 
> Currently ATA_EH_FASTDRAIN_INTERVAL is 3 secs which should be enough
> for finishing up most commands.
> 
> Signed-off-by: Tejun Heo <htejun@gmail.com>

what type of errors are we talking about?  device errors can be handled 
on a more granular basis than other errors.