[PATCH v4 1/2] Kconfig: add btrfs to distro boot

[Matthias Brugger <mbrugger@suse.com>]

On 27/01/2020 22:58, Tom Rini wrote:
> On Fri, Jan 17, 2020 at 08:59:02PM +0100, matthias.bgg at kernel.org wrote:
> 
>> From: Matthias Brugger <mbrugger@suse.com>
>>
>> Some distributions use btrfs as the default file system.
>> Enable btrfs support by default when using distro boot for all
>> architectures but riscv, as it breaks compilation due to size problems.
>>
>> Signed-off-by: Matthias Brugger <mbrugger@suse.com>
> 
> This adds around 60kb to many platforms, so I'm not going to take this
> right now.  But I'm not rejecting it outright.  My question however is,
> I was under the impression that the direction distributions were taking
> was that bootefi would be used to start GRUB2 and that (and its
> filesystem modules) would be responsible for doing the next steps.  So
> we wouldn't need btrfs support here for example as everything would be
> picked out of the system partition, which is FAT32.   Am I mistaken
> about the flow here?  Thanks!
> 

I think the assumption is correct for most of the distributions (if not all).
However in distro boot we support e.g. extlinux/sysboot which not necessarily
boots a EFI binary. Apart from that, think about a broken system partition. In
that case if your distribution has the kernel on a btrfs partition, you would
not be able to boot this kernel.
That's the reason why we enable ext2 and ext4 support in distro boot.

Regarding the size, I'm aware of the problem, that's why it is set as imply in
Kconfig so that individual boards can turn it off. We might think about chaning
ext2 and ext4 from select to imply as well as we are at the limit on some platforms.

Regards,
Matthias

Regards,
Matthias