From: greg <greg@lonnon.org>
To: roland <for_spam@gmx.de>
Cc: user-mode-linux-devel@lists.sourceforge.net
Subject: Re: [uml-devel] mounting COW on HOST?
Date: Mon, 08 Dec 2003 19:10:08 -0700 [thread overview]
Message-ID: <1070935808.4256.25.camel@profx.lonnon.org> (raw)
In-Reply-To: <009701c3bded$d0efef70$2000000a@schlepptopp>
Roland,
It wouldn't be that tough to write a COW block device for the standard
kernel. In fact, if we did that, we could get rid of the COW hack in
the ubd device.
The basic idea of COW is a bitmap to represent all the sectors of the
block device, a backing block device and a cow block device. Any
blocking device should work.
I have also thought of changing the index to be a 4 byte offset, this
would useful for live CD distros with a floppy device. The floppy
device becomes the COW disk while the backing file is the CDROM. I
haven't done the math on the usability of 1.4MB floppy or the recovery
mechanism in case of a kernel panic, etc... But having a live CD in
which any sector could be changed might be interesting, at least make it
easier for the live CD people.
See ya,
Greg
On Mon, 2003-12-08 at 17:45, roland wrote:
> hi!
> one thing came to my mind today: why not porting the COW feature of UML to
> the "mainstream" linuxkernel itself?
> i would find this useful - not only in relation to UML.
> maybe there is already something like this? don`t know....
> what would we need? modifying loopdevice(mount -o loop...) code? perhaps using
> lufs for that? (btw: long awaited read/write support for ntfs partitions has
> been implemented via lufs and native windows ntfs.sys driver!)
> maybe this has been discussed already?
>
> regards
> roland
>
>
>
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next prev parent reply other threads:[~2003-12-09 2:10 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-12-09 0:45 [uml-devel] mounting COW on HOST? roland
2003-12-09 2:10 ` greg [this message]
2003-12-09 3:58 ` Russell Coker
2003-12-09 2:18 ` Matt Zimmerman
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