[systemd-devel] [PATCH/resend] Use reflinking to copy kernel

[Zbigniew Jędrzejewski-Szmek]

On Mon, May 18, 2015 at 02:15:09PM +0200, Lennart Poettering wrote:
> On Sat, 16.05.15 22:16, Zbigniew Jędrzejewski-Szmek (zbyszek at in.waw.pl) wrote:
> 
> > On Fri, May 08, 2015 at 05:11:15PM -0400, Josh Boyer wrote:
> > > On May 8, 2015 11:38 AM, "Zbigniew Jędrzejewski-Szmek" <zbyszek at in.waw.pl>
> > > wrote:
> > > >
> > > > On Thu, May 07, 2015 at 10:08:56PM -0400, Matthew Miller wrote:
> > > > > On Thu, May 07, 2015 at 04:29:11PM -0500, Ian Pilcher wrote:
> > > > > > Hmm.  If don't know off the top of my head if Fedora cloud images
> > > have a
> > > > > > separate /boot or not, but disk space is a big concern in such
> > > > > > environments.
> > > > >
> > > > > They don't have a separate boot, fwiw.
> > > > What about amending the patch to use
> > > >
> > > >    cp --reflink=auto ...
> > > >
> > > > ?
> > > 
> > > The kernel-install tool is what would need to be patched. It is what is
> > > doing the copying at install time.  Doing it in the spec is pointless as
> > > we're mucking around in the build root not the actual system.
> > Strictly speaking, using --reflink=auto would be useful in the spec
> > too, to avoid copying the files. In a build root it is very likely to
> > succeed too.
> > 
> > But you're right of course, it's kernel-install that counts.
> > 
> > Patches for kernel-install and dracut attached.
> > 
> > [Since this patch is for systemd, resending it to systemd-devel. I should
> > have done in the first place. If intend to push it in a few days if nobody
> > objects.]
> 
> --reflink=auto is the default in cp since a while. Instead of
> cluttering systemd's or dracut's trees with it, I'd rather recommend
> upgrading coreutils as necessary.
I don't think that's true. With today's git, without --reflink=auto,
cp does a normal read() + write(). I think the default for mv is to use
reflink though.

Zbyszek