I did the make-it-a-union thing. Seems OK.
Hugh Dickins <[email protected]> wrote:
>
> +#if NR_CPUS >= CONFIG_SPLIT_PTLOCK_CPUS
> +/*
> + * We tuck a spinlock to guard each pagetable page into its struct page,
> + * at page->private, with BUILD_BUG_ON to make sure that this will not
> + * overflow into the next struct page (as it might with DEBUG_SPINLOCK).
> + * When freeing, reset page->mapping so free_pages_check won't complain.
> + */
> +#define __pte_lockptr(page) ((spinlock_t *)&((page)->private))
> +#define pte_lock_init(_page) do { \
> + BUILD_BUG_ON((size_t)(__pte_lockptr((struct page *)0) + 1) > \
> + sizeof(struct page)); \
> + spin_lock_init(__pte_lockptr(_page)); \
> +} while (0)
> +#define pte_lock_deinit(page) ((page)->mapping = NULL)
> +#define pte_lockptr(mm, pmd) ({(void)(mm); __pte_lockptr(pmd_page(*(pmd)));})
> +#else
Why does pte_lock_deinit() zap ->mapping? That doesn't seem to have
anything to do with anything?
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