Currently "btrfstune --csum" allows us to change the csum to the same
one, this is good for testing but not good for end users, as if the end
user interrupts it, they have to resume the change (even it's to the
same csum type) until it finished, or kernel would reject such fs.
Furthermore, we never change the super block csum type until we
completely changed the csum type, thus for resume cases, the fs would
still show up as using the old csum type thus won't cause any problem
resuming.
So here we just reject the csum conversion if the target csum type is
the same as the existing csum type.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
4d5711f4dd