Re: [PATCH v2] Use full btrfs bootloader area

[Daniel Kiper]

On Mon, Dec 13, 2021 at 02:25:49PM +0800, Michael Chang via Grub-devel wrote:
> Up to now GRUB can only embed to the first 64 KiB before primary
> superblock of btrfs, effectively limiting the size that could
> consequently pose restrictions to feature enablement like advanced zstd
> compression.
>
> This patch attempts to utilize full unused area reserved by btrfs for
> bootloader outlined in the document [1] where this paragraph quoted.
>
> "The first 1MiB on each device is unused with the exception of primary
> superblock that is on the offset 64KiB and spans 4KiB."
>
> Apart from that, adjacent sectors to superblock and first block group
> are not used for embedding in case of overflow and logged access to
> adjacent sectors could be useful to tracing it up.
>
> This patch has been tested to provide out of the box support to btrfs
> zstd compression with which GRUB has been installed to the partition.
>
> [1] 
> https://btrfs.wiki.kernel.org/index.php/Manpage/btrfs(5)#BOOTLOADER_SUPPORT
>
> Signed-off-by: Michael Chang <mchang@suse.com>

Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

Daniel