Re: [PATCH] ext4 extent support

[Felix Zielcke]

From: "Bean" <address@hidden>
Sent: Sunday, July 06, 2008 6:51 AM
To: "The development of GRUB 2" <address@hidden>
Subject: Re: [PATCH] ext4 extent support

> I found the description of flex_bg:
>
> This feature relaxes check restrictions on where each block groups meta 
> data is
> located within the storage media. This allows for the allocation of 
> bitmaps or
> inode tables outside the block group boundaries in cases where bad blocks 
> forces
> us to look for new blocks which the owning block group can not satisfy. 
> This
> will also allow for new meta-data allocation schemes to improve 
> performance and
> scalability.
>
> The reallocation only occurs when bad blocks force us to use another
> block group, which is quite rare. So we should silently ignore this
> flag.

Hm, I just saw that there's a next branch in Tytso's ext4 git tree [1]
I always looked at the normal HEAD tree or whatever it's called on git, I 
don't know much about git slang :)
There in Documentation/filesystems/ext4.txt it says:

* ability to pack bitmaps and inode tables into larger virtual groups via 
the flex_bg feature
* Inode allocation using large virtual block groups via flex_bg

mke2fs man page [2] says:

Allow bitmaps and inode tables for a block group to be placed anywhere
on the storage media (use with -G option to group meta-data in order
to create a large virtual block group).

But because I don't know what that exactly means I'm not sure if GRUB code 
needs to be a bit changed for it or not :)

[1] 
http://git.kernel.org/?p=linux/kernel/git/tytso/ext4.git;a=tree;h=next;hb=next
[2] 
http://git.kernel.org/?p=fs/ext2/e2fsprogs.git;a=blob;f=misc/mke2fs.8.in;hb=HEAD