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Message-ID: <20081205183657.GC2144@kroah.com>
Date: Fri, 5 Dec 2008 10:36:57 -0800
From: Greg KH <greg@...ah.com>
To: Tejun Heo <tj@...nel.org>
Cc: Greg KH <gregkh@...e.de>, Theodore Ts'o <tytso@....edu>,
Zwane Mwaikambo <zwane@....linux.org.uk>,
torvalds@...ux-foundation.org, Eugene Teo <eteo@...hat.com>,
Justin Forbes <jmforbes@...uxtx.org>,
linux-kernel@...r.kernel.org,
Chris Wedgwood <reviews@...cw.f00f.org>,
Domenico Andreoli <cavokz@...il.com>,
Randy Dunlap <rdunlap@...otime.net>, Willy Tarreau <w@....eu>,
Michael Krufky <mkrufky@...uxtv.org>, alan@...rguk.ukuu.org.uk,
Chuck Ebbert <cebbert@...hat.com>,
Jeff Garzik <jgarzik@...hat.com>,
Dave Jones <davej@...hat.com>, akpm@...ux-foundation.org,
Jake Edge <jake@....net>,
Chuck Wolber <chuckw@...ntumlinux.com>, stable@...nel.org,
Rodrigo Rubira Branco <rbranco@...checkpoint.com>
Subject: Re: [stable] [patch 067/104] libata: improve phantom device
detection
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@...nel.org>
> >
> > 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@...nel.org>
> > Signed-off-by: Jeff Garzik <jgarzik@...hat.com>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
>
> 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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