Re: [PATCH RESEND 0/3] scsi: fix internal write cache issue on usbhdd.
From: Greg KH
Date: Mon Jul 16 2012 - 19:48:23 EST
On Sat, Jul 07, 2012 at 11:04:45PM -0400, Namjae Jeon wrote:
> From: Namjae Jeon <namjae.jeon@xxxxxxxxxxx>
> 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.
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