On Sun, Dec 16, 2001 at 04:34:01PM +0100, Christoph Rohland wrote:
> Hi David,
>
> On Fri, 14 Dec 2001, David Gibson wrote:
> >> But the core of shmem is always compiled. And the rest is as simple
> >> as ramfs...
> >
> > The point of keeping ramfs simple isn't to reduce the kernel image
> > size, it's to keep it useful as an example of how to make a trivial
> > filesystem.
>
> >From this point of view I prefer the oversimplified version in the
> stock kernel. We should probably correct the comment about missing
> features like limits and timestamps and tag it as experimental. But
> IMHO this version explains the underlying concept best.
>
>
> If we want a useable ramfs implementation we should try to keep the
> image size down and try to make it as similar to tmpfs as
> possible. This would keep the administrators overhead low.
>
> I append two cummulative patches against 2.4.17-rc1 (only slightly
> tested):
>
> 1) Add removepage to the addresspace_operations to simplify
> shmem.c. This is taken from your ramfs limits patch.
> 2) Add support for a ramfs2 filesystem type to shmem.c. The only
> feature missing compared to ramfs + limits are loopback devices on
> top of ramfs files. It does not add memory need compared to
> ramfs. Have a look how small this is.
I don't think there's a lot of point playing with this in 2.4.x. In
2.5 it depends a bit on what changes to the VFS happen. I recall that
near the end of the 2.3 cycle Al Viro proposed a change to add
essentially a removepage operation (he called it detachpage IIRC) - he
was using it to eliminate a bunch of the "if (page->buffers)" tests.
I don't know it that's still on the cards - it so it could certainly
simplify both ramfs and shmfs.
-- David Gibson | For every complex problem there is a david@gibson.dropbear.id.au | solution which is simple, neat and | wrong. -- H.L. Mencken http://www.ozlabs.org/people/dgibson- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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