Re: [PATCH] initrd: support erofs as initrd

["hch@lst.de" <hch@lst.de>]

On Fri, Mar 21, 2025 at 01:17:54PM +0000, Julian Stecklina wrote:
> Of course there are some solutions to using erofs images at boot now:
> https://github.com/containers/initoverlayfs
> 
> But this adds yet another step in the already complex boot process and feels
> like a hack. It would be nice to just use erofs images as initrd. The other
> building block to this is automatically sizing /dev/ram0:
> 
> https://lkml.org/lkml/2025/3/20/1296
> 
> I didn't pack both patches into one series, because I thought enabling erofs
> itself would be less controversial and is already useful on its own. The
> autosizing of /dev/ram is probably more involved than my RFC patch. I'm hoping
> for some input on how to do it right. :)

Booting from erofs seems perfectly fine to me.  Booting from erofs on
an initrd is not.  There is no reason to fake up a block device, just
have a version of erofs that directly points to pre-loaded kernel
memory instead.  This is a bit more work, but a lot more efficient
in that it removes the block path from the I/O stack, removes the boot
time copy and allows for much more flexible memory management.