[RFC] Add XFS support in SYSLINUX

[Christoph Hellwig]

Hi Chen,

thanks a lot for your interested in tackling this project.

Writing to the end of the first block would work for 4k or larger block
sizes filesystems, but it's not a very clean solution.

Id had a quick brainstorm with Dave and we came up with the following
idea:

 - create an extended attribute on the root filesystem that is larger
   than than the filesystem block size (typically 4k), and store the
   syslink payload in it.
 - for the first prototype get its block number using the GETBMAPX
   ioctl, and use it.

once that prototype works we can talk about a good interface for you.
We could precreate the attribute at mkfs time at a fixed block number
so that syslinux can hardcode it, or we could discuss any other kind
of interface that helps you.