mm/cma: introduce interface for early reservations

It can be desirable to reserve memory in a CMA area before it is
activated, early in boot.  Such reservations would effectively be memblock
allocations, but they can be returned to the CMA area later.  This
functionality can be used to allow hugetlb bootmem allocations from a
hugetlb CMA area.

A new interface, cma_reserve_early is introduced.  This allows for
pageblock-aligned reservations.  These reservations are skipped during the
initial handoff of pages in a CMA area to the buddy allocator.  The caller
is responsible for making sure that the page structures are set up, and
that the migrate type is set correctly, as with other memblock allocations
that stick around.  If the CMA area fails to activate (because it
intersects with multiple zones), the reserved memory is not given to the
buddy allocator, the caller needs to take care of that.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Frank van der Linden <[email protected]>
Cc: Alexander Gordeev <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Dan Carpenter <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Joao Martins <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Madhavan Srinivasan <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Oscar Salvador <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Roman Gushchin (Cruise) <[email protected]>
Cc: Usama Arif <[email protected]>
Cc: Vasily Gorbik <[email protected]>
Cc: Yu Zhao <[email protected]>
Cc: Zi Yan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

1 files changed, 9 insertions, 0 deletions

diff --git a/mm/mm_init.c b/mm/mm_init.c
index 3eec528afe43..b5047c5ef7d6 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -2263,6 +2263,15 @@ void __init init_cma_reserved_pageblock(struct page *page)
 	adjust_managed_page_count(page, pageblock_nr_pages);
 	page_zone(page)->cma_pages += pageblock_nr_pages;
 }
+/*
+ * Similar to above, but only set the migrate type and stats.
+ */
+void __init init_cma_pageblock(struct page *page)
+{
+	set_pageblock_migratetype(page, MIGRATE_CMA);
+	adjust_managed_page_count(page, pageblock_nr_pages);
+	page_zone(page)->cma_pages += pageblock_nr_pages;
+}
 #endif
 
 void set_zone_contiguous(struct zone *zone)