[syslinux] "EDD Load error" on btrfs, how to debug?

[Paulo Alcantara]

On Tue, May 20, 2014 1:52 pm, Anatol Pomozov wrote:

> Ok, we've figured out potential cause of the problem. The next
> question how to minimize the size of ldlinux.sys?
>
> BTW looking at official (?) binary
> https://www.kernel.org/pub/linux/utils/boot/syslinux/Testing/6.03/syslinux-6.03-pre11.tar.xz
> I see that their size is also more than 64K

Actually, there is *no* 64KiB limit on btrfs. Look at btrfs-progs
(ctree.h:830):

"
/*
 * We don't want to overwrite 1M at the beginning of device, even though
 * there is our 1st superblock at 64k. Some possible reasons:
 *  - the first 64k blank is useful for some boot loader/manager
 *  - the first 1M could be scratched by buggy partitioner or somesuch
 */
#define BTRFS_BLOCK_RESERVED_1M_FOR_SUPER	((u64)1024 * 1024)
"

1MiB seems to be a reasonable size to fit bootsector + LDLINUX.SYS in. I
don't know exactly how Syslinux is handling this, but it should be using
the whole available space (1MiB instead).

-- 
Paulo Alcantara, C.E.S.A.R
Speaking for myself only.