rbtree: adjust root color in rb_insert_color() only when necessary
authorMichel Lespinasse <walken@google.com>
Mon, 8 Oct 2012 23:30:44 +0000 (16:30 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Tue, 9 Oct 2012 07:22:33 +0000 (16:22 +0900)
commit6d58452dc066db61acdff7b84671db1b11a3de1c
tree36df08157d975398c5416d068f83cd31b79ae2c7
parent1f0528653e41ec230c60f5738820e8a544731399
rbtree: adjust root color in rb_insert_color() only when necessary

The root node of an rbtree must always be black.  However,
rb_insert_color() only needs to maintain this invariant when it has been
broken - that is, when it exits the loop due to the current (red) node
being the root.  In all other cases (exiting after tree rotations, or
exiting due to an existing black parent) the invariant is already
satisfied, so there is no need to adjust the root node color.

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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
lib/rbtree.c