rbtree: add some additional comments for rebalancing cases

While overall the code is very nicely commented, it might not be
immediately obvious from the diagrams what is going on.  Add a very
brief summary of each case.  Opposite cases where the node is the left
child are left untouched.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Davidlohr Bueso <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Davidlohr Bueso 2017-09-08 16:14:42 -07:00 • committed by Linus Torvalds
commit 35dc67d7d9

View file

@ -132,7 +132,7 @@ __rb_insert(struct rb_node *node, struct rb_root *root,
if (parent != tmp) { /* parent == gparent->rb_left */
if (tmp && rb_is_red(tmp)) {
/*
* Case 1 - color flips
* Case 1 - node's uncle is red (color flips).
*
* G g
* / \ / \
@ -155,7 +155,8 @@ __rb_insert(struct rb_node *node, struct rb_root *root,
tmp = parent->rb_right;
if (node == tmp) {
/*
* Case 2 - left rotate at parent
* Case 2 - node's uncle is black and node is
* the parent's right child (left rotate at parent).
*
* G G
* / \ / \
@ -179,7 +180,8 @@ __rb_insert(struct rb_node *node, struct rb_root *root,
}
/*
* Case 3 - right rotate at gparent
* Case 3 - node's uncle is black and node is
* the parent's left child (right rotate at gparent).
*
* G P
* / \ / \