Re: [stable] [patch 067/104] libata: improve phantom devicedetection

[Greg KH]

On Thu, Dec 04, 2008 at 01:20:15PM +0900, Tejun Heo wrote:
> > 2.6.27-stable review patch.  If anyone has any objections, please let us know.
> > 
> > ------------------
> > From: Tejun Heo <tj@xxxxxxxxxx>
> > 
> > commit 6a6b97d360702b98c02c7fca4c4e088dcf3a2985 upstream.
> > 
> > Currently libata uses four methods to detect device presence.
> > 
> > 1. PHY status if available.
> > 2. TF register R/W test (only promotes presence, never demotes)
> > 3. device signature after reset
> > 4. IDENTIFY failure detection in SFF state machine
> > 
> > Combination of the above works well in most cases but recently there
> > have been a few reports where a phantom device causes unnecessary
> > delay during probe.  In both cases, PHY status wasn't available.  In
> > one case, it passed #2 and #3 and failed IDENTIFY with ATA_ERR which
> > didn't qualify as #4.  The other failed #2 but as it passed #3 and #4,
> > it still caused failure.
> > 
> > In both cases, phantom device reported diagnostic failure, so these
> > cases can be safely worked around by considering any !ATA_DRQ IDENTIFY
> > failure as NODEV_HINT if diagnostic failure is set.
> > 
> > Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
> > Signed-off-by: Jeff Garzik <jgarzik@xxxxxxxxxx>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
> 
> Alan thinks this patch could cause regression.  Given that we're
> nearing the end of 2.6.28-rc cycles, I don't think it's critical to
> include this into 2.6.27-stable or at least it can wait a bit more.

Ok, I'll transfer it over to the next 2.6.27-stable release.

thanks,

greg k-h
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