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authorMichel Lespinasse <walken@google.com>2012-10-08 16:30:32 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-10-09 16:22:32 +0900
commit4c199a93a2d36b277a9fd209a0f2793f8460a215 (patch)
treeb7d6af9220ef445eb4a9f5f0966a3bc5306fe513 /lib
parent1457d2877864d918c546735bd89c29d5e2a542f1 (diff)
downloadvexpress-lsk-4c199a93a2d36b277a9fd209a0f2793f8460a215.tar.gz
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 commit 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 commit 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. [sfr@canb.auug.org.au: fix net/ceph/osd_client.c build] Signed-off-by: Michel Lespinasse <walken@google.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Acked-by: David Woodhouse <David.Woodhouse@intel.com> Cc: Rik van Riel <riel@redhat.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Daniel Santos <daniel.santos@pobox.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: John Stultz <john.stultz@linaro.org> Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/rbtree.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/lib/rbtree.c b/lib/rbtree.c
index d4175565dc2..fe43c8c5f52 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