rbtree: low level optimizations in __rb_erase_color()

rbtree: low level optimizations in __rb_erase_color()

In __rb_erase_color(), we often already have pointers to the nodes being
rotated and/or know what their colors must be, so we can generate more
efficient code than the generic __rb_rotate_left() and __rb_rotate_right()
functions.

Also when the current node is red or when flipping the sibling's color,
the parent is already known so we can use the more efficient
rb_set_parent_color() function to set the desired color.

Signed-off-by: Michel Lespinasse <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Acked-by: David Woodhouse <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Daniel Santos <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: "Eric W. Biederman" <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>