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Date: Thu, 2 Dec 2010 09:17:37 -0500
From: Christoph Hellwig <hch@infradead.org>
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Subject: Re: [linux-lvm] Bugs in mkfs.xfs, device mapper, xfs, and /dev/ram
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To: Spelic <spelic@shiftmail.org>
Cc: Christoph Hellwig <hch@infradead.org>, linux-lvm@redhat.com, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, xfs@oss.sgi.com

On Thu, Dec 02, 2010 at 03:14:28PM +0100, Spelic wrote:
> On 12/02/2010 03:11 PM, Christoph Hellwig wrote:
> >I'm pretty sure you have CONFIG_DEBUG_BLOCK_EXT_DEVT enabled.  This
> >option must never be enabled, as it causes block devices to be
> >randomly renumered.  Together with the ramdisk driver overloading
> >the BLKFLSBUF ioctl to discard all data it guarantees you to get
> >data loss like yours.
> 
> Nope...
> 
> # CONFIG_DEBUG_BLOCK_EXT_DEVT is not set

Hmm, I suspect dm-linear's dumb forwarding of ioctls has the same
effect.