On Wed, May 02, 2018 at 05:26:39PM +0000, Matthew Wilcox wrote:
> Option 2:
>
> @@ -113,9 +113,14 @@ struct page {
> struct kmem_cache *slub_cache; /* shared with slab */
> /* Double-word boundary */
> void *slub_freelist; /* shared with slab */
> - unsigned inuse:16;
> - unsigned objects:15;
> - unsigned frozen:1;
> + union {
> + unsigned long counters;
> + struct {
> + unsigned inuse:16;
> + unsigned objects:15;
> + unsigned frozen:1;
> + };
> + };
> };
> struct { /* Tail pages of compound page */
> unsigned long compound_head; /* Bit zero is set */
>
> Pro: Expresses exactly what we do.
> Con: Back to five levels of indentation in struct page
The indentation issue can be fixed (to some extend) by declaring the union
outside struct page and just use it inside.
I don't advocate for the approach, just listing the option.
--
Kirill A. Shutemov
