mm: Make compound_pincount always available

Move compound_pincount from the third page to the second page, which
means it's available for all compound pages.  That lets us delete
hpage_pincount_available().

On 32-bit systems, there isn't enough space for both compound_pincount
and compound_nr in the second page (it would collide with page->private,
which is in use for pages in the swap cache), so revert the optimisation
of storing both compound_order and compound_nr on 32-bit systems.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 43fb3155298e..785d6e340292 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1320,7 +1320,9 @@ static void __destroy_compound_gigantic_page(struct page *page,
 	}
 
 	set_compound_order(page, 0);
+#ifdef CONFIG_64BIT
 	page[1].compound_nr = 0;
+#endif
 	__ClearPageHead(page);
 }
 
@@ -1812,7 +1814,9 @@ out_error:
 	for (; j < nr_pages; j++, p = mem_map_next(p, page, j))
 		__ClearPageReserved(p);
 	set_compound_order(page, 0);
+#ifdef CONFIG_64BIT
 	page[1].compound_nr = 0;
+#endif
 	__ClearPageHead(page);
 	return false;
 }