On Thu, Nov 05, 2020 at 04:51:42PM -0800, Ralph Campbell wrote:
Add a helper function to allow device drivers to create device private transparent huge pages. This is intended to help support device private THP migrations.
I think you'd be better off with these calling conventions:
-void prep_transhuge_page(struct page *page) +struct page *thp_prep(struct page *page) { + if (!page || compound_order(page) == 0) + return page; /* - * we use page->mapping and page->indexlru in second tail page + * we use page->mapping and page->index in second tail page * as list_head: assuming THP order >= 2 */ + BUG_ON(compound_order(page) == 1);
INIT_LIST_HEAD(page_deferred_list(page)); set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR); + + return page; }
It simplifies the users.
+void prep_transhuge_device_private_page(struct page *page) +{
- prep_compound_page(page, HPAGE_PMD_ORDER);
- prep_transhuge_page(page);
- /* Only the head page has a reference to the pgmap. */
- percpu_ref_put_many(page->pgmap->ref, HPAGE_PMD_NR - 1);
+} +EXPORT_SYMBOL_GPL(prep_transhuge_device_private_page);
Something else that may interest you from my patch series is support for page sizes other than PMD_SIZE. I don't know what page sizes your hardware supports. There's no support for page sizes other than PMD for anonymous memory, so this might not be too useful for you yet.