Re: [linux 2.6 patch] ext2 support for hurd extensions via xattr interface

[Roland McGrath]

> Just curious, would it not make sense to have this for ext3, too? After
> all, one can mount ext3 filesystems as ext2 on GNU/Hurd (AFAIK), 

As I understand it, it is true that an ext3 filesystem with its journal
files fully replayed or whatnot that constitutes "fully clean" state, is a
valid ext2 filesystem.  So to that extent, yes.  However, note that this
code is specifically for ext2 filesystems with "creator os" set to "hurd".
This functionality is of no use whatsoever on your random ext[23]
filesystems created for use with GNU/Linux--those formats as usually
created (i.e. without `mke2fs -o hurd') do represent the Hurd-specific
information and using such filesystems on the Hurd will not give you the
ability to record passive translator or author information.

Hence, I don't see it as useful to put this support into the Linux ext3
code as well.  Furthermore, that code is written so as to duplicate tons of
ext2 code and data structures identically with all the 2s changed to 3s.
While I endeavor to contribute code in the form desired by its maintainers
and take existing practice as evidence of what that is, this pointless
duplication is not something I felt like engaging in.  It is most certainly
counterproductive while the code is still being tested and debugged.

> I tried using star, but I get errors when I try to extract /gnu/servers.
> I am not sure whether this is expected to work at all, though, as I get
> EOPNOTSUPP.

Did you compile with CONFIG_EXT2_FS_XATTR_HURD=y?
Is the filesystem in question an ext2 filesystem with creator `hurd'?
If you created it on GNU/Linux and didn't use `mke2fs -o hurd', then the
answer is no.

> strace:
> [...]
> setxattr("gnu/servers/exec", "gnu.translator", 0x808c110, 11, ) = -1 
> EOPNOTSUPP (Operation not supported)
> [...]

> I then tried to debug star [...]

The strace output gave you all the information you need to know.
star did the right thing, and the kernel said no dice.

> Sorry if I might have totally missed the point,

Possible.  If there is not a FAQ entry around for "Is your ext2 filesystem
format able to passive translators?", there should be.