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Date: Mon, 30 Jul 2001 15:50:33 -0500 (CDT)
From: Jeff Garzik <jgarzik@mandrakesoft.com>
To: Mike Touloumtzis <miket@bluemug.com>
cc: Alexander Viro <viro@math.psu.edu>, linux-kernel@vger.kernel.org,
        Linus Torvalds <torvalds@transmeta.com>, linux-fsdevel@vger.kernel.org
Subject: Re: [CFT] initramfs patch
In-Reply-To: <20010730132957.A20284@bluemug.com>
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On Mon, 30 Jul 2001, Mike Touloumtzis wrote:
> On Mon, Jul 30, 2001 at 02:05:55AM -0400, Alexander Viro wrote:
> > The thing unpacks cpio archive (currently - linked into the kernel image)
> > on root ramfs and execs /init. After that we are in userland code. Said
> > code (source in init/init.c and init/nfsroot.c) emulates the vanilla
> > 2.4 behaviour. You can replace it with your own - that's just the default
> > that gives (OK, is supposed to give) a backwards-compatible behaviour.
> 
> One thing that would make embedded systems developers very happy
> is the ability to map a romfs or cramfs filesystem directly from
> the kernel image, avoiding the extra copy necessitated by the cpio
> archive.  Are there problems with this approach?

Yes -- you need to at that point store initialized structures.  Store
the dcache in its unpacked state on the ROM image, etc.  That's the only
way to "map" a romfs directly.  Otherwise there is ALWAYS an unpacking
or translation step between filesystem image and in-memory image.

Mapping an in-memory image directly may seem like a good idea, but it is
really not.  ESPECIALLY for embedded folks.

Use a programmatic solution to unpack your filesystem... like say cpio
format in initramfs. :)

	Jeff



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