> the pointers are always going to be aligned. So let's just use the
> lowest bit of the parent pointer instead. This shrinks the rb_node from
> 4 machine-words to 3.
We've seen this patch before, haven't we? :) I still like it.
> Another pair of eyes on the 'remove dead code in rb_erase()' bit in
> particular would be appreciated.
I'll trade you some eyes for a description beyond the four words
obvious, remove, dead, and code.
> struct rb_node
> {
> - struct rb_node *rb_parent;
> - int rb_color;
> + unsigned long rb_parent_colour;
How about some kerneldoc comments?
> #define RB_RED 0
> #define RB_BLACK 1
> +#define rb_colour(r) ((r)->rb_parent_colour & 1)
This creates a pretty strong bond between the two.. maybe a
RB_COLOUR_MASK and use that and the _RED/_BLACK defines instead of the
raw constants?
> +#define rb_is_red(r) (!rb_colour(r))
> +#define rb_is_black(r) rb_colour(r)
> +#define rb_set_red(r) do { (r)->rb_parent_colour &= ~1; } while (0)
> +#define rb_set_black(r) do { (r)->rb_parent_colour |= 1; } while (0)
> +
> +static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
> +{
BUG_ON((unsigned long)p & 3);
> + rb->rb_parent_colour = (rb->rb_parent_colour & 3) | (unsigned long)p;
> +}
> +static inline void rb_set_colour(struct rb_node *rb, int colour)
> +{
> + rb->rb_parent_colour = (rb->rb_parent_colour & ~1) | colour;
> +}
> +
> #define RB_ROOT (struct rb_root) { NULL, }
> #define rb_entry(ptr, type, member) container_of(ptr, type, member)
>
> @@ -131,8 +147,7 @@ extern void rb_replace_node(struct rb_no
> static inline void rb_link_node(struct rb_node * node, struct rb_node * parent,
> struct rb_node ** rb_link)
> {
> - node->rb_parent = parent;
> - node->rb_color = RB_RED;
> + node->rb_parent_colour = (unsigned long )parent;
use rb_set_parent(node, parent) and get the assertion.
- z
-
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