[RFC] Add XFS support in SYSLINUX

[RFC] Add XFS support in SYSLINUX

[CHEN Baozi]

Hi all,

I'm a student applying for this year's GSoC and planning to add XFS support to the syslinux bootloader. I did some research on the syslinux's implementation, and have a rough idea. 

XFS starts its superblock from the first bytes of partition, where syslinux would install its boot codes(in the first 512 bytes). Currently, we have two approach to handle that. One is to follow the GRUB that put its codes in the first few bytes immediately following the MBR and before the first partition's first sector. However, this approach breaks some designing rules of syslinux, so it won't be accepted. The other one that we are now considering is to use the remaining 2048 bytes left in XFS's first block. But I'm not sure that this area is reserved for some new features in the future. 

Any comment?

Regards,
Chen Baozi
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Re: [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.

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Re: [RFC] Add XFS support in SYSLINUX

[CHEN Baozi]

Thanks for advice:-) 

Baozi
On Apr 3, 2012, at 2:48 AM, Christoph Hellwig wrote:

> 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.
> 

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