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Date: Tue, 17 Jul 2012 08:46:53 -0700
From: Greg KH <gregkh@linuxfoundation.org>
To: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Namjae Jeon <linkinjeon@gmail.com>, mdharm-usb@one-eyed-alien.net,
        stern@rowland.harvard.edu, sshtylyov@mvista.com, bvanassche@acm.org,
        akpm@linux-foundation.org, linux-usb@vger.kernel.org,
        linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org,
        Namjae Jeon <namjae.jeon@samsung.com>
Subject: Re: [PATCH RESEND 0/3] scsi: fix internal write cache issue on usb
 hdd.
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On Tue, Jul 17, 2012 at 08:19:14AM +0100, James Bottomley wrote:
> On Mon, 2012-07-16 at 16:48 -0700, Greg KH wrote:
> > On Sat, Jul 07, 2012 at 11:04:45PM -0400, Namjae Jeon wrote:
> > > From: Namjae Jeon <namjae.jeon@samsung.com>
> > > 
> > > The numbers of USB HDDs(All USB HDD I checked) does not respond
> > > correctly to scsi mode sense command for retrieving the write cache
> > > page status. Even though write cache is enabled by default, due to
> > > scsi driver assume that cache is not enabled which in turn might lead
> > > to loss of data since data still will be in cache.
> > > This result that all filesystems is not stable on USB HDD when the
> > > device is unplugged abruptly, even though these are having journaling
> > > feature. Our first trying is that scsi driver send ATA command
> > > (ATA Pass through, #85) to USB HDD after failure from normal routine to
> > > know write cache enable.
> > > We have known it is dangerous after testing several USB HDD. some of
> > > HDD is stalled by this command(A-DATA HDD). So we tried to make the
> > > patch James Bottomley's suggestion(usb quirk) on version 2 that add
> > > product ID and verdor ID of USB HDD to USB quirk list after checking
> > > write cache.
> > > All filesystem will be stable on USB HDD registered in quirk list.
> > > And it will be updated continuously.
> > 
> > Now applied to the usb-next branch.
> 
> It's been in scsi#misc for ten days with no problems.  Lets leave it
> there rather than create merge and rebase issues.

No need for rebasing.  It's already in my tree, so we can handle the
merge when this hits Linus's tree.

thanks,

greg k-h