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/20170719014603.19029-4-dave@stgolabs.net Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -132,7 +132,7 @@ __rb_insert(struct rb_node *node, struct rb_root *root,
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if (parent != tmp) { /* parent == gparent->rb_left */
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if (parent != tmp) { /* parent == gparent->rb_left */
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if (tmp && rb_is_red(tmp)) {
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if (tmp && rb_is_red(tmp)) {
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/*
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/*
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* Case 1 - color flips
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* Case 1 - node's uncle is red (color flips).
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*
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*
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* G g
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* G g
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* / \ / \
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* / \ / \
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@ -155,7 +155,8 @@ __rb_insert(struct rb_node *node, struct rb_root *root,
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tmp = parent->rb_right;
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tmp = parent->rb_right;
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if (node == tmp) {
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if (node == tmp) {
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/*
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/*
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* Case 2 - left rotate at parent
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* Case 2 - node's uncle is black and node is
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* the parent's right child (left rotate at parent).
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*
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*
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* G G
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* G G
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* / \ / \
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* / \ / \
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@ -179,7 +180,8 @@ __rb_insert(struct rb_node *node, struct rb_root *root,
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}
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}
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/*
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/*
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* Case 3 - right rotate at gparent
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* Case 3 - node's uncle is black and node is
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* the parent's left child (right rotate at gparent).
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*
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*
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* G P
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* G P
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* / \ / \
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* / \ / \
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