In case 1, it passes down the BLACK color from G to p and u, and maintains
the color of n.  By doing so, it maintains the black height of the
sub-tree.
While in the comment, it marks the color of n to BLACK.  This is a typo
and not consistents with the code.
This patch fixs this typo in comment.
Signed-off-by: Wei Yang <weiyang@linux.vnet.ibm.com>
Acked-by: Michel Lespinasse <walken@google.com>
Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
                                 *      / \          / \
                                 *     p   u  -->   P   U
                                 *    /            /
-                                *   n            N
+                                *   n            n
                                 *
                                 * However, since g's parent might be red, and
                                 * 4) does not allow this, we need to recurse