commit 0d95c1be upstream.

The sizes that are obtained from space infos are in raw units and have
to be adjusted according to the raid factor. This was missing for
f_bavail and df reported doubled size for raid1.
Reported-by: Martin Steigerwald <Martin@lichtvoll.de>
Fixes: ba7b6e62 ("btrfs: adjust statfs calculations according to raid profiles")
Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>