Re: [PATCH] i386-pc: build btrfs zstd support into separate module

[Daniel Kiper]

On Tue, Aug 31, 2021 at 03:12:28PM +0800, Michael Chang via Grub-devel wrote:
> The zstd support in btrfs brings significant size increment to the
> on-disk image that it can no longer fit into btrfs bootloader area and
> short mbr gap.
>
> In order to support grub update on outstanding i386-pc setup with these
> size constraints remain in place, here we build the zstd suppprt of
> btrfs into a separate module, named btrfs_zstd, to alleviate the size
> change. Please note this only makes it's way to i386-pc, other
> architecture is not affected.

I am OK with extracting zstd code from btrfs code. However, I want that be
done for all architectures and platforms. No exceptions.

[...]

> diff --git a/grub-core/fs/btrfs_zstd.c b/grub-core/fs/btrfs_zstd.c
> new file mode 100644
> index 000000000..d5d1e013c
> --- /dev/null
> +++ b/grub-core/fs/btrfs_zstd.c
> @@ -0,0 +1,36 @@
> +/*
> + *  GRUB  --  GRand Unified Bootloader
> + *  Copyright (C) 2008  Free Software Foundation, Inc.
> + *
> + *  GRUB is free software: you can redistribute it and/or modify
> + *  it under the terms of the GNU General Public License as published by
> + *  the Free Software Foundation, either version 3 of the License, or
> + *  (at your option) any later version.
> + *
> + *  GRUB is distributed in the hope that it will be useful,
> + *  but WITHOUT ANY WARRANTY; without even the implied warranty of
> + *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + *  GNU General Public License for more details.
> + *
> + *  You should have received a copy of the GNU General Public License
> + *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include <grub/types.h>
> +#include <grub/dl.h>
> +/* For NULL.  */
> +#include <grub/mm.h>
> +#include <grub/btrfs.h>
> +#include <grub/lib/zstd.h>
> +
> +GRUB_MOD_LICENSE ("GPLv3+");
> +
> +GRUB_MOD_INIT (btrfs_zstd)
> +{
> +  grub_btrfs_zstd_decompress_func = grub_zstd_decompress;

Please create a function in btrfs module which will do this for you.

> +}
> +
> +GRUB_MOD_FINI (btrfs_zstd)
> +{
> +  grub_btrfs_zstd_decompress_func = NULL;

Ditto.

Last but not least, please CC original author of zstd support next time.

Daniel