ext3 compatibility between 2.4 and 2.6 kernels
adilger at clusterfs.com
Tue Feb 22 17:26:46 UTC 2005
On Feb 22, 2005 09:47 -0700, Howdy Pierce wrote:
> Thanks for your prompt help. The problem (as you hinted) turned out
> to be SELinux.
> So -- the extended attributes get turned on using SE Linux, and this
> happens regardless of whether you use the -Onouser_xattr flag to
The user_xattr flag only allows/prevents regular users from storing EAs
to the filesystem.
> When I disabled SE Linux and repeated the test, the dumpe2fs from
> before and after the mount/tar/umount was more similar. Also,
> symbolic links were now readable from a 2.4 kernel, and my embedded
> system boots correctly (and finds init).
I would guess that /sbin/init is a symlink then?
> I can't say I really understand enough about SE Linux to have an
> opinion as to whether this is a bug or not. It seems like there
> should be some option, even on an SE Linux system, to write ext2/3
> filesystems in a backward-compatible manner.
Note that EAs (generally, this EA-on-symlink problem being an unfortunate
exception) are compatible with older kernels. This functionality was
added after EAs were developed and added to the kernel already.
I agree it might be useful to have an option to prevent any EAs from
being stored on a filesystem, since this also consumes space in the
filesystem that has no value to your embedded device. I don't think
that mounting the filesystem as ext2 will help as it also has EA support.
As I mentioned previously, it is possible with a tiny patch to the 2.4
kernel to fix ext3_inode_is_fast_symlink() to understand symlinks with EAs.
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