Christoph Lameter <[email protected]> wrote:
>
> This undoes the optimization that resulted in a yield in do_swap_cache().
> do_swap_cache() stays as is. Instead we convert the migration entry to
> a page * in lookup_swap_cache.
>
> For the non swap case we need a special macro version of lookup_swap_cache
> that is only capable of handling migration cache entries.
>
> ...
>
> @@ -305,6 +306,12 @@ struct page * lookup_swap_cache(swp_entr
> {
> struct page *page;
>
> + if (is_migration_entry(entry)) {
> + page = migration_entry_to_page(entry);
> + get_page(page);
> + return page;
> + }
What locking ensures that the state of `entry' remains unaltered across the
is_migration_entry() and migration_entry_to_page() calls?
>
> +/*
> + * Must use a macro for lookup_swap_cache since the functions
> + * used are only available in certain contexts.
> + */
> +#define lookup_swap_cache(__swp) \
> +({ struct page *p = NULL; \
> + if (is_migration_entry(__swp)) { \
> + p = migration_entry_to_page(__swp); \
> + get_page(p); \
> + } \
> + p; \
> +})
hm. Can nommu do any of this?
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