From f95f5391de57b23b8a672e5c73ac7bae78ee2032 Mon Sep 17 00:00:00 2001 From: Michel Lespinasse Date: Fri, 7 Sep 2012 10:23:45 +1000 Subject: [PATCH] rbtree: empty nodes have no color Empty nodes have no color. We can make use of this property to simplify the code emitted by the RB_EMPTY_NODE and RB_CLEAR_NODE macros. Also, we can get rid of the rb_init_node function which had been introduced by 88d19cf37952 ("timers: Add rb_init_node() to allow for stack allocated rb nodes") to avoid some issue with the empty node's color not being initialized. I'm not sure what the RB_EMPTY_NODE checks in rb_prev() / rb_next() are doing there, though. axboe introduced them in 10fd48f2376d ("rbtree: fixed reversed RB_EMPTY_NODE and rb_next/prev"). The way I see it, the 'empty node' abstraction is only used by rbtree users to flag nodes that they haven't inserted in any rbtree, so asking the predecessor or successor of such nodes doesn't make any sense. One final rb_init_node() caller was recently added in sysctl code to implement faster sysctl name lookups. This code doesn't make use of RB_EMPTY_NODE at all, and from what I could see it only called rb_init_node() under the mistaken assumption that such initialization was required before node insertion. Signed-off-by: Michel Lespinasse Cc: Andrea Arcangeli Acked-by: David Woodhouse Cc: Rik van Riel Cc: Peter Zijlstra Cc: Daniel Santos Cc: Jens Axboe Cc: "Eric W. Biederman" Cc: John Stultz Signed-off-by: Andrew Morton --- fs/proc/proc_sysctl.c | 4 +--- include/linux/rbtree.h | 15 +++++---------- include/linux/timerqueue.h | 2 +- lib/rbtree.c | 4 ++-- 4 files changed, 9 insertions(+), 16 deletions(-) diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c index dfafeb2b05a0..a93dec45b6b7 100644 --- a/fs/proc/proc_sysctl.c +++ b/fs/proc/proc_sysctl.c @@ -168,10 +168,8 @@ static void init_header(struct ctl_table_header *head, head->node = node; if (node) { struct ctl_table *entry; - for (entry = table; entry->procname; entry++, node++) { - rb_init_node(&node->node); + for (entry = table; entry->procname; entry++, node++) node->header = head; - } } } diff --git a/include/linux/rbtree.h b/include/linux/rbtree.h index e6a807720ded..2049087c43b7 100644 --- a/include/linux/rbtree.h +++ b/include/linux/rbtree.h @@ -67,17 +67,12 @@ static inline void rb_set_color(struct rb_node *rb, int color) #define RB_ROOT (struct rb_root) { NULL, } #define rb_entry(ptr, type, member) container_of(ptr, type, member) -#define RB_EMPTY_ROOT(root) ((root)->rb_node == NULL) -#define RB_EMPTY_NODE(node) (rb_parent(node) == node) -#define RB_CLEAR_NODE(node) (rb_set_parent(node, node)) +#define RB_EMPTY_ROOT(root) ((root)->rb_node == NULL) + +/* 'empty' nodes are nodes that are known not to be inserted in an rbree */ +#define RB_EMPTY_NODE(node) ((node)->rb_parent_color == (unsigned long)(node)) +#define RB_CLEAR_NODE(node) ((node)->rb_parent_color = (unsigned long)(node)) -static inline void rb_init_node(struct rb_node *rb) -{ - rb->rb_parent_color = 0; - rb->rb_right = NULL; - rb->rb_left = NULL; - RB_CLEAR_NODE(rb); -} extern void rb_insert_color(struct rb_node *, struct rb_root *); extern void rb_erase(struct rb_node *, struct rb_root *); diff --git a/include/linux/timerqueue.h b/include/linux/timerqueue.h index 5088727478fd..a520fd70a59f 100644 --- a/include/linux/timerqueue.h +++ b/include/linux/timerqueue.h @@ -39,7 +39,7 @@ struct timerqueue_node *timerqueue_getnext(struct timerqueue_head *head) static inline void timerqueue_init(struct timerqueue_node *node) { - rb_init_node(&node->node); + RB_CLEAR_NODE(&node->node); } static inline void timerqueue_init_head(struct timerqueue_head *head) diff --git a/lib/rbtree.c b/lib/rbtree.c index d4175565dc2c..fe43c8c5f527 100644 --- a/lib/rbtree.c +++ b/lib/rbtree.c @@ -387,7 +387,7 @@ struct rb_node *rb_next(const struct rb_node *node) { struct rb_node *parent; - if (rb_parent(node) == node) + if (RB_EMPTY_NODE(node)) return NULL; /* If we have a right-hand child, go down and then left as far @@ -416,7 +416,7 @@ struct rb_node *rb_prev(const struct rb_node *node) { struct rb_node *parent; - if (rb_parent(node) == node) + if (RB_EMPTY_NODE(node)) return NULL; /* If we have a left-hand child, go down and then right as far -- 2.39.5