incomapt inline xattr between ext2 and ext4 used for ext2

Hi there,

For a ext2 disk with 256B inode size, if mount it with ext4 driver(ext4 
used for ext2), file xattr will be stored in inode if it fits. And then 
if we mount this disk on a system only with old ext2 filesystem driver, 
the xattr will be lost since old ext2 driver doesn't support xattr in inode.

This seems an incompat issue, is this a problem or by design? Or maybe 
we should set sbi->s_want_extra_isize to 0 if EXTRA_ISIZE feature is not 
enabled.

I know ext2 driver has already been deprecated however this use case 
seems still exist in some old setup's upgrade/downgrade scenarios.

Thanks.

-- 
Regards